Module 1
Nature of Physical Geography
A. Definition of Physical Geography
Physical Geography is the study of spatial distributions of phenomena across the
landscape, processes that created and changed those distributions, and implications for
those distributions on people. Geography is both a natural and a social science.
Geographers think broadly, emphasizing interconnections and complex issues, solving
complicated problems such as resource management, environmental impact assessment,
spread of disease, and urban planning. Although many such occupations do not have the
title of geographer, they require a geographic perspective. Let’s have a closer look at
what the geographic perspective entails.
Geographers approach problems from different perspectives than other natural
and social scientists. Specifically, geographers think spatially, meaning they emphasize
the setting, such as location, in addressing problems, and holistically, integrating ideas
from a wide variety of the natural and social sciences. In many ways, it is not what is
studied that makes it geography, but instead how it is studied. The decision of whether to
drill for oil in Alaska’s Arctic National Wildlife Refuge (ANWR) is a complicated issue
that can be best understood using the geographic approach.
Physical Geography study diverse problems, ranging from weather systems and
climate change to ocean currents and landscape evolution. The types of data required to
investigate each of these problems are equally diverse, but most geographers try to
approach the problem in a similar, objective way, guided by spatial information and
relying on various geographic tools. Geography utilizes approaches from the natural and
social sciences, blending them together in a geographic approach. Like other scientists,
geographers pose questions about natural phenomena and their implications, propose a
possible explanation (hypothesis) that can be tested, make predictions from this
hypothesis, and collect data needed to critically evaluate whether the hypothesis passes
the tests.
The conceptual basis of these questions lies in the notion that the location of
something affects, and is a product of, other features or processes in both the natural and
human environment, and of interactions between the natural and human environments.
Natural and human phenomena are constantly changing and constantly impacting other
features in new ways, influencing aspects like site selection and risk of natural hazards.
To address such complex issues, we use a variety of tools and methods, such as maps,
computer-simulation models, aerial photographs, satellite imagery, statistical methods,
and historical records. The figure to the right illustrates some aspects to consider.
Geographers approach problems in many ways, asking questions about Earth
processes and collecting data that help answer these questions. Some questions can be
answered with qualitative data, but others require quantitative data, which are numeric
and are typically visualized and analyzed using data tables, calculations, equations, and
graphs. Science proceeds as scientists explore the unknown — making observations and
then systematically investigating questions that arise from observations that are puzzling
or unexpected. Often, we try to develop several possible explanations and then devise
ways to test each one. The normal steps in this scientific method are illustrated below,
using an investigation of groundwater contaminated by gasoline.
B. Operation of Natural Systems
Earth has a number of systems in which matter and energy are moved or
transformed. These involve processes of the solid Earth, water in all its forms, the
structure and motion of the atmosphere, and how these three domains (Earth, water, and
air) influence life. Such systems are dynamic, responding to any changes in conditions,
whether those changes arise internally within the system or are imposed externally from
outside the system.
Earth consists of four overlapping spheres — the atmosphere, biosphere,
hydrosphere, and lithosphere — each of which interacts with the other three spheres. The
atmosphere is mostly gas, but includes liquids (e.g., water drops) and solids (e.g., ice and
dust). The hydrosphere represents Earth’s water, and the lithosphere is the solid Earth.
The biosphere includes all the places where there is life — in the atmosphere, on and
beneath the land, and on and within the oceans.
Many aspects of Earth can be thought of as a system — a collection of matter,
energy, and processes that are somehow related and interconnected. For example, an air-
conditioning system consists of some mechanical apparatus to cool the air, ducts to carry
the cool air from one place to another, a fan to move the air, and a power source. There
are two main types of systems: open systems and closed systems. Systems consist of
matter and energy, and they respond to internally or externally caused changes in matter
and energy, as a tree responds to a decrease in rain (matter) or colder temperatures during
the winter (energy). Systems can respond to such changes in various ways, either
reinforcing the change or counteracting the change.
Matter and energy move within and between each of the four spheres. A
fundamental principle of all natural sciences is that energy and matter can be neither
created nor destroyed, but only transferred from one form to another — the First Law of
Thermodynamics. A second principle is that energy and matter tend to become dispersed
into a more uniform spatial distribution — the Second Law of Thermodynamics. As a
result, matter and energy are stored, moved, dispersed, and concentrated as part of natural
cycles, in which material and energy move back and forth among various sites within the
four spheres.
Atmospheric processes involve the redistribution of energy and matter from one
part of the atmosphere to another. Moving air masses have momentum, which can be
transferred from one object to another. Storage and transfer of energy are the drivers of
Earth’s climate and weather. Energy can be moved from one part of the atmosphere to
another, such as by air currents associated with storms. Also, energy is released or
extracted from the local environment when water changes from one state of matter to
another, such as from a liquid to a gas.
Water in all of its forms, along with other matter, moves globally, tending to
disperse, but other factors prevent an even spatial distribution. As a result, some regions
are more humid and cloudy than others, as shown in this satellite image of water vapor
(blue is more, brown is less). Also, water cycles between vapor, liquid, and solid states.
Moving air masses have mass and velocity, so they have momentum, which is defined as
mass times velocity. A dense, fast-moving dust storm has more momentum than a gentle
breeze in dust-free air. Winds near the surface are slowed by interactions with trees, hills,
buildings, etc. Winds aloft are faster and can transfer their momentum downward.
Many processes in the Earth occur as part of a cycle, a term that describes the
movement of matter and energy between different sites in Earth’s surface, subsurface,
and atmosphere. The most important of these is the hydrologic cycle, which involves
local-to-global-scale storage and circulation of water and associated energy near Earth’s
surface. Matter and energy are also stored and moved on Earth’s surface and subsurface.
The rock cycle, summarized below and discussed in more detail later, describes the
movement of matter and energy on and below Earth’s surface at timescales from seconds
to billions of years, involving such processes as erosion, burial, melting, and uplift of
mountains.
Rock is broken apart or altered by chemical reactions when exposed to sunlight,
rain, wind, plants, and animals. This weathering creates loose pieces of rock called
sediment. Sediment is then stripped away by erosion, and moved (transported) by gravity,
glaciers, flowing water, or wind. After transport, the sediment is laid down, or deposited,
at any point along the way, such as beside the stream, or when it reaches a lake or the sea.
Sediment is eventually buried, compacted by the weight of overlying sediment, and
perhaps cemented together by chemicals in the water to form a harder rock. A rock
exposed to high temperatures may melt and become molten, forming magma. As magma
cools, either at depth or after being erupted onto the surface, it begins to crystallize and
solidify into rock. Deep rocks may be uplifted back to the surface where they are again
exposed to weathering.
The biosphere includes life and all of the places it exists. It overlaps the
atmosphere, hydrosphere, and lithosphere, extending from more than 10 kilometers above
the surface to more than 10 kilometers beneath sea level, both on the seafloor and within
Earth’s subsurface. Life interacts with the other three spheres, forming a number of
important cycles, several of which are described later. Plants exchange gases with the
atmosphere. They extract carbon dioxide (CO2 ) from the atmosphere and use the carbon
for their leaves, stems, roots, spines, and other leafy or woody parts. Plants also release
oxygen, a key ingredient in life. Life on Earth is currently the main source of the oxygen
and CO2 in the atmosphere.
The Sun is the ultimate source of energy for photosynthesis, as well as movement
of matter and energy in the atmosphere and most movement of material on Earth’s
surface. Life interacts with the hydrologic cycle. Plants take in water from the rocks and
soil, which may have arrived from lakes and other bodies of surface water, or directly
from the atmosphere, as during precipitation. Plants then release some water back into the
environment. Life also interacts with aspects of the rock cycle. Plants help break down
materials on Earth’s surface, such as when a plant root pushes open fractures in rocks and
soil. Plants help stabilize soils, inhibiting erosion, by slowing down the flow of water,
allowing it to remain in contact with rocks and soil longer. This increases the rate at
which weathering breaks down materials. Humans have altered the surface of Earth by
removing vegetation that would compete with crops, villages, and cities. Water, nutrients,
and other materials are stored and cycled through the biosphere, at local to global scales.
We use the term biogeochemical cycle to indicate that plants, animals, and bacteria, in
addition to chemical and physical processes, are involved in the cycling of a chemical
substance through different parts of the environment. For example, the movement of
carbon between the biosphere, atmosphere, hydrosphere, and lithosphere is a
biogeochemical cycle known as the carbon cycle.
C. Earth’s Four Spheres
There are various expressions of these interactions, many of which we can
observe in our daily lives. In addition to natural interactions, human activities, such as the
clearing of forests, can affect interactions between the spheres. Changes in one
component of one sphere can cause impacts that affect components of other spheres. The
four spheres interact in complex and sometimes unanticipated ways. As you read each
example below, think of other interactions — observable in your typical outdoor
activities — that occur between each pair of spheres. The Sun’s energy evaporates water
from the ocean and other parts of the hydrosphere, moving the water molecules into the
atmosphere. The water vapor can remain in the atmosphere or can condense into tiny
drops that form most clouds. Under certain conditions, the water returns to the surface as
precipitation.
Active volcanoes emit gases into the atmosphere, and major eruptions release
huge quantities of steam, sulfur dioxide, carbon dioxide, and volcanic ash. In contrast,
weathering of rocks removes gas and moisture from the atmosphere. Precipitation
accumulates on the land, where it can form standing water, groundwater, or erosion-
causing runoff. Plants and animals utilize precipitation from the atmosphere, and some
plants can extract moisture directly out of the air without precipitation. Broad-scale
circulation patterns in the atmosphere are a principal factor in determining an area’s
climate, and the climate directly controls the types of plants and animals that inhabit a
region.
Channels within a stream generally bend back and forth as the water flows
downhill. The water is faster and more energetic in some parts of the stream than in
others, and so erodes into the streambed and riverbank. In less energetic sections,
sediment will be deposited on the bed, like the gravel in this photograph. Earth’s surface
can be uplifted or dropped down, as during an earthquake, and the resulting changes can
influence the balance of erosion and deposition. Oceans contain a diversity of life, from
whales to algae, and everything in between. Coral reefs represent an especially life-rich
environment, formed when living organisms extract materials dissolved in or carried by
seawater to produce the hard parts of corals, shells, and sponges. At greater ocean depths,
where waters are colder, shells and similar biological materials dissolve, transferring
material back to the seawater. The clearest interaction between the lithosphere and
biosphere is the relationship between plants and soils. The type of soil helps determine
the types of plants that can grow, and in turn depends on the types of starting materials
(rocks and sediment), the geographic setting of the site (e.g., slope versus flat land),
climate, and other factors. Plants remove nutrients from the soil but return material back
to the soil through roots and annual leaf fall, or plant death and decay.
Anyone who has flown in an airplane or spent some time using Google Earth®
appreciates the amazing amount of human influence on the landscape. The intent of
development is almost always to improve the human condition, but the complex chain
reaction of impacts that cascade through the system can cause unintended and often
harmful impacts elsewhere in one or more of the four spheres, as illustrated in the
examples below. Some consequences of human impacts are not felt immediately but only
appear much later, after the activity has continued for many years.
Humans clear forests, a critical part of the biosphere, to provide lumber and grow
food. In addition to the loss of habitat for plants and animals, deforestation reduces the
amount of CO2 that can be extracted out of the atmosphere and stored in the carbon-rich
trunks, branches, and leaves of plants. Removing plant cover also causes increased
runoff, which enhances soil erosion and leads to the additional loss of plant cover — an
unintended consequence and a positive feedback.
Over 80,000 dams exist in the U.S., providing water supplies, generating
electricity, protecting towns from flooding, and providing recreational opportunities.
Dams also alter the local water balance by interrupting the normal seasonal variations in
flows of water and by capturing silt, sand, wood, and other materials that would normally
go downstream. Construction and filling of the reservoir disrupts ecosystems, displaces
people, and threatens or destroys plant and animal communities. Local warming of the
atmosphere occurs near cities because of normal urban activities (lighting, heating, etc.)
and because many urban materials, like dark asphalt, capture and store more heat than
natural open space. Heat is also released from car exhausts and industrial smokestacks.
Non-natural drainage systems cause rapid accumulation and channeling of water.
Development infringes on natural plant and animal communities, disturbs or covers soil,
and alters erosion rates.
D. Earth’s Surface
Earth’s surface displays various features, including mountains, hillslopes, and
river valleys. We commonly represent such features on the land surface of an area with a
topographic map or shaded-relief map, each of which is useful for certain purposes. Some
maps allow us to visualize the landscape and navigate across the land, whereas others
permit the quantitative measurement of areas, directions, and steepness of slopes. Maps
are the primary way we portray the land surface. Some maps depict the shape and
elevation of the land surface, whereas others, like a soil map, represent the materials on
that surface. Views of SP Crater in northern Arizona provide a particularly clear example
of the relationship between the land surface and different types of maps.
This perspective view has aerial photography superimposed over topography
(shape of the land). What features do you observe in the topography? Which areas are
high in elevation? What are the most distinctive features? Take a minute to observe this
scene before reading on. The area has distinct, cone-shaped hills surrounded by broad,
less steep areas. The hills are small volcanoes, which formed when fragments of molten
rock were ejected into the air and settled around a volcanic vent.
In the center of the area is a nearly black feature, which is a solidified lava flow
formed when fluid magma erupted onto the surface in the last 5,000 years. The volcano at
the southern end of the lava flow is named SP Crater, and is well known to many physical
geographers. Examine other features in the scene. Note the light-gray areas in the upper
left parts of the image, and the linear features formed by fractures that cut across the gray
rocks. Different materials are forming different types of landscapes. This entire area has a
relatively dry climate, with few trees to obscure the landform features.
Earth’s surface is not flat and featureless, but instead has high and low parts.
Topography is steep in some areas but nearly flat in others. We use common terms to
refer to the height of the land and the steepness of slopes. The height of a feature above
sea level is its elevation. Scientists describe elevation in meters (m) or kilometers (km)
above sea level, but some maps and most signs in the U.S. list elevation in feet (ft).
Beneath water, we talk about depth, generally expressing it as depth below sea level. We
use meters for shallow depths and kilometers for greater ones. We also refer to the height
of a feature above an adjacent valley. The difference in elevation of one feature relative
to another is topographic relief. Like elevation, we measure relief in meters or feet; we
refer to rugged areas as having high relief and to flatter areas as having low relief.
One way to represent the topography of an area, especially the steepness of the
land surface, is to envision an imaginary slice through a terrain, like this one through SP
Crater (⊲). The dark line shows the change in elevation across the land surface, and is a
topographic profile. Cliffs and slopes that drop sharply in elevation are steep slopes,
whereas topography that is less steep is referred to as being gentle, as in a gentle slope.
We describe steepness of a slope in degrees from horizontal. The eastern slope of SP
Crater has a 26-degree slope (26° slope). We also talk about gradient—a 26° slope drops
480 meters over a distance of one kilometer, typically expressed as 480 m /1,000 m or
simply as 0.48.
E. Latitude and Longitude
Imagine trying to describe the location of an “X” on a featureless sphere. What
system would you devise to convey the location? If the sphere did not have any markings
or seams, we would need to first establish a frame of reference — a place on the sphere
from which to reference the location of the X. For these reasons, we have devised
systems of imaginary gridlines on the Earth. These are referenced as angles from the
known points within or on the Earth. The most commonly used imaginary gridlines are
latitude and longitude, which are displayed on many maps and are provided by the
location capabilities of many cellular phones.
If you were trying to convey the location of the X on the sphere, or the location of
a city on our nearly spherical planet, a good place to begin visualizing the problem is to
establish a framework of imaginary gridlines. Another important aspect is to consider
how lines and planes interact with a sphere. We could draw lines that circle the globe,
each staying the same distance from the North or South Pole. The lines are parallel to one
another and remain the same distance apart, and so are called parallels. In addition, these
lines are parallel to imaginary cuts through the Earth, perpendicular to Earth’s spin axis
(which goes through the North and South Poles). The parallel that is halfway between the
North and South Pole is the equator. If we traveled along one of these lines (i.e., along a
parallel), we would stay at the same distance from the pole as we encircled the planet. In
other words, our position in a north-south framework would not change.
Lines that encircle the globe from North Pole to South Pole are called meridians.
Meridians do not stay the same distance apart and are not parallel. Instead, meridians are
widest at the equator and converge toward each pole. A meridian would be the path you
would travel if you took the most direct route from the North Pole to the South Pole, or
from south to north. The term meridian comes from a Latin term for midday because the
Sun is along a meridian (i.e., is due south or north) at approximately noon. The terms
A.M. (for before noon) and P.M. (for after noon) are also derived from this Latin term
(e.g., post meridiem).
The intersection of a plane and a sphere is a curved, circular line that encircles the
sphere. If the plane is constrained to pass through the center of the sphere, we call the
resulting intersection a great circle. A great circle also represents the shortest distance
between two points on a sphere and so is the path airlines travel over long distances. A
great circle divides the sphere into two equal halves. The equator is a great circle,
separating the Earth into two hemispheres — the Northern Hemisphere north of the
equator and the Southern Hemisphere south of the equator. A north-south oriented great
circle is used to separate the Western Hemisphere, which includes North and South
America, from the Eastern Hemisphere, which includes Europe, Asia, Africa, and
Australia. Antarctica, over the South Pole, and the Arctic Ocean, over the North Pole,
each straddle the great circle between the Eastern Hemisphere and Western Hemisphere.
An imaginary plane that intersects a sphere without going through Earth’s center
is called a small circle. As is obvious from the small circle illustrated in this figure, a
small circle does not divide the globe into equal halves. Note that all parallels, which are
oriented east-west, are small circles, except the equator, which is a great circle (it divides
the planet into two equal halves). In contrast, each north-south meridian, when paired
with its counterpart on the other side of the globe, forms a great circle. Any such pair of
meridians divides the globe into two equal halves. When viewed together, parallels and
meridians divide the planet into a grid of somewhat rectangular regions. Such regions
encompass greater area near the equator than near the poles, due to the convergence of
meridians toward the poles.
If you were a pilot flying from New York City to Moscow, Russia, how would
you know which way to go? Our imaginary grid of parallels and meridians provides a
precise way to indicate locations using latitude and longitude, which are expressed in
degrees. Fractions of a degree are expressed as decimal degrees (e.g., 9.73°) or as
minutes and seconds, where there are 60 minutes (indicated by ') in a degree and 60
seconds (") in a minute (e.g., 9° 43' 48").
The latitude of a location indicates its position north or south of the equator. Lines
of latitude are parallels that encircle the globe east-west. The angle created by drawing
lines connecting the position of an object on the Earth’s surface to the center of the Earth,
and then to the equator, defines the number of degrees of latitude of the object’s position.
In the Northern Hemisphere, latitude is expressed as degrees north. In the Southern
Hemisphere, latitude is expressed as degrees south or as negative degrees. Parallels of
latitude run east-west around the Earth. The zero line of latitude is the equator, with the
values increasing to 90 at the north and south poles. There are ten million meters from the
equator to the North and South Poles, so one degree of latitude is approximately 111 km
(69 miles). In addition to the equator, there are a few lines of latitude that are especially
important. These include the Tropic of Cancer and Tropic of Capricorn, which are 23.5°
north and south of the equator, respectively. Also important are the Arctic Circle and
Antarctic Circle, which are 66.5° north and south of the equator (23.5° away from the
corresponding pole). As discussed later, the 23.5° angle is how much the Earth’s axis is
tilted with respect to the Sun.
The longitude of a location indicates its east-west position. Lines of longitude are
meridians that encircle the globe north-south. As a starting point, a zerodegree meridian
is defined as the north-south line that passes through Greenwich, U.K. — this is called
the Prime Meridian. The angle created by the object’s position, the center of the Earth,
and the Prime Meridian defines that object’s longitude, given as degrees east or west of
the Prime Meridian. Meridians west of the Prime Meridian often are expressed as
negative degrees. Meridians of longitude run north-south. They are widest at the equator
(where a degree of longitude is also about 111 km) and converge at higher latitudes until
they meet at the poles. Starting at the zero meridian through Greenwich, values increase
toward 180° E and 180° W as they approach the International Date Line, an imaginary
line that runs through the middle of Pacific Ocean (not shown; on the opposite side of the
globe).
We use other systems besides latitude and longitude to describe location. These
include the Universal Transverse Mercator (UTM) system, the State Plane Coordinate
System (SPCS), and the Public Land Survey System (PLSS). Each is very useful for
certain applications, and some are used to specify the location of real-estate properties
appearing on legal documents associated with purchasing a house. Therefore, they are
relevant to most citizens, even those who are not geographers.
Maps can show large regions, even the entire world. The main considerations for
displaying large regions arise mostly from the fact that we live on a three-dimensional
world (a sphere) and flat maps are two-dimensional. One solution to this challenge is the
Universal Transverse Mercator (UTM) system, a method of identifying locations across
the nonpolar part of the Earth. UTM is the most useful method of location for people who
frequently hike or camp, or for people who work outdoors in nonurban setting. The UTM
system slices the nonpolar region into 60 north-south zones, each 6° of longitude wide.
The slices are numbered from 1 to 60, with numbers increasing eastward from the
International Date Line. A slice comprises two UTM zones, one in the Northern
Hemisphere and another in the Southern Hemisphere. For example, most of Florida is in
UTM zone 17 N, whereas the southern tip of South America is mostly in UTM Zone 19
S. What is the UTM zone for the place where you grew up or go to school?
The slices are further subdivided into grid zones, each 20° of latitude long, as
shown by the rectangles on this map. The purpose of UTM zones is to ensure that
location is portrayed accurately in the middle of each division, as distortion increases
toward the edges. Due to large distortions that occur in the UTM system near the poles,
UTMs are typically only used between 80° N and 80° S latitudes (we generally do not
use UTM within 10° of the poles). . For a location within a grid zone, we specify
coordinates as eastings and northings. Eastings are a measure of the number of meters
east or west of the central meridian for that zone. Northings are a measure of the position
north or south of the equator. The map below shows the aerial photograph of the horse
and cow pasture shown earlier in this chapter, but this time with a UTM grid labeled with
eastings (along the bottom of the map) and northings (along the left side of the map).
The advantage of the UTM system is that it is a “square” grid system measured in
meters rather than degrees, so it is convenient for measuring direction and distance. Note
how useful this grid and UTM system would be if you were riding around trying to
record the location of each horse in the pasture. Two horses (not visible here) are grazing
at an easting of 495250 and a northing of 4214100; can you determine about where these
horses are? Are they in the green pasture? We can specify locations using several
systems, and convert from one location system to another. The map above shows the
position of a site expressed in both latitude-longitude (commonly called “lat-lon”) and
UTM coordinates. There are Internet sites that allow easy conversion from lat-lon to
UTM and vice versa. To go from UTM to lat-lon, you have to specify the UTM zone,
which can be determined using the large map near the top of this page.
The State Plane Coordinate System (SPCS) is a third system for mapping, used
only in the U.S. SPCS ignores the distortion caused by the curvature of the Earth by
treating the surface as a plane, so it should only be used for smaller areas like states or
parts of states. As a result, the system can use X-Y coordinates to represent positions,
simplifying land surveys and calculations of distances and areas. Another advantage is
that the projection was chosen based on the geographic orientation of the state or section
of the state, to minimize distortion for that area.
In the SPCS, most states are subdivided into two or more zones called state plane
zones; some states are a single zone. Alaska has 10 zones and Hawaii has five zones. The
boundaries of the zones generally are east-west or north-south, but are not straight,
following local county boundaries (trying to keep a county within a single zone). States
that are elongated east-west, such as Tennessee, use different map approaches to generate
the state plane coordinates than states like Illinois that are elongated north-south. The
goal is to customize the drawing of the map so as to minimize the distortion that is
always present when trying to show features of a spherical Earth on a flat piece of paper.
So local U.S. maps, such as for flood zones, roads, or property delineation, are likely to
use the SPCS. If you buy a house in the U.S., the legal documents will likely use SPCS to
specify the location of the property, perhaps accompanied by a survey in UTM.
The Public Land Survey System (PLSS) is another system used in the U.S. for
describing the location of lands and for subdividing larger land parcels into smaller ones.
When you hear someone refer to a “section of land” or a “quarter-section,” they are
talking about PLSS. The PLSS is also called the township-range system. The Public Land
Survey System was designed specifically for public lands, such as those administered by
the U.S. Department of the Interior, and as a result is most widely used in states where
there are federal lands. It is not used in many eastern states, where there is little land that
is not privately owned, and in Texas, which has much state-owned land. These two
regions are shown in yellow.
PLSS is based around some initial point. From this point, a Principal Meridian
extends both north and south and a Base Line extends both east and west. Beginning at
the Principal Meridian, the land is subdivided into six-mile-wide, north-south strips of
land called ranges. Beginning at the Base Line, the land is subdivided into six-milewide,
east-west strips of land called townships.
Each square of the township-range grid is six miles in an east-west direction and
six miles in a north-south direction, so it is 36 mi2 in area. Each grid square is further
subdivided into 36 sections that are each one square mile in area. Township and range
lines and section boundaries are included on many topographic maps. Each one-square-
mile section can be further divided into quarters, eighths, and even smaller subdivisions.
The rectangle in the southeastern corner of Section 14 would be described as being in the
eastern half of the southeast quarter of Section 14, Township 2 South and Range 3 East.
This is abbreviated: E1/2 SE1/4, S. 14, T2S, R3E.
F. Map Projections
Earth is not flat, so a flat map cannot portray all locations accurately. An ideal
map would preserve directions, distances, shapes, and areas, but it is not possible to
preserve all four of these accurately. Instead, either the shape of features on a map, such
as country outlines, is preserved or the area of features is preserved, but never both at the
same time. Many map projections depict both shape and area somewhat inaccurately, as a
trade-off, so that neither will be shown more inaccurately. Cartographers (map makers)
have developed different ways of projecting our three- dimensional world onto a flat
map, and each approach is called a map projection. The particular type of projection is
chosen based on the intended use of the map.
A map projection is a mathematical algorithm used to represent places on a three-
dimensional spherical Earth on a flat map. Imagine shining a light through a partially
transparent globe and observing the image projected on the back wall. This is what a map
projection does, but in a quantitative way. While many projections exist, the best
projection for a given map will introduce the least distortion for the key areas being
shown. Whenever a map is made, some distortion is introduced by the projection. It is
impossible to avoid distorting either shapes or areas, or doing some distortions of each.
Perhaps the easiest projection to visualize conceptually is to imagine peeling an
orange and slicing it in a few strategic places to allow it to be flattened without buckling.
Sinusoidal projections work on this same premise. If the map can be interrupted so that
areas of lesser significance for a given application are not shown, then less distortion
exists in the areas that are shown. Straight, parallel lines remain so, and have their correct
length. Meridians become progressively longer toward the edges of each lobe of the map.
While areas are preserved, shape distortion increases near the edges of each lobe.
The shape distortion problem in such projections can be mitigated by increasing
the number of central meridians around which accuracy is preserved. However, this
comes at the expense of having more areas of interrupted coverage. Notice how the
central meridians are straightest and appear at right angles to the parallels at the equator.
These are the areas that are depicted most accurately for this type of projection. The most
common type of map using this projection strategy is called a Goode projection.
In cylindrical projections, the globe is transformed to a flat page by projecting a
globe outward onto a cylinder. The projection starts at a line, called the standard line,
where the globe touches the cylinder, usually at the equator. These types of map
projections have no distortion at the standard line (equator), but distortion becomes worse
with increasing distance from the standard line. The resulting maps portray parallels of
latitude as straight lines with the same length as the equator (that is, distorted in length)
and depicts meridians also as straight lines intersecting the parallels at right angles.
Cylindrical projections (⊳) depict compass directions as straight lines, so they are
excellent for navigation. However, because the meridians are depicted (falsely) as being
parallel to each other, east-west exaggeration of distances is severe, particularly in high
latitudes. To allow these maps to be conformal (preserve shapes), north-south distances
are stretched to match the east-west exaggeration. This makes high-latitude areas greatly
exaggerated in size, but they retain shapes. High-latitude distortion increases to such an
extent that the poles cannot be shown. The most familiar type of cylindrical projection is
the Mercator map, which became an important tool in the Age of Exploration. The part of
the map at the right, which is a Mercator projection, portrays Greenland as being larger
than the conterminous U.S. Is this true? Some maps blend aspects of a cylindrical map
with other types of projections. The Robinson projection is a commonly used projection
of a world map, especially in textbooks. It does not fully preserve areas or shapes, instead
representing a compromise between conformal and equal-area projections. The meridians
curve gently, and the parallels are straight lines horizontally across the map. A feature it
shares with cylindrical maps is severe distortion near the poles.
Conical projections involve conceptualizing a cone over the globe, usually with
the apex of the cone vertically above the pole. No distortion occurs along the arc where
the globe touches the cone— the standard line, usually a parallel of latitude. If the cone
slices through the globe and intersects the surface along two arcs (usually parallels of
latitude), the projection is called polyconical. In either case, distortion increases with
distance away from these arcs. In conical projections, parallels are concentric circles and
meridians are lines radiating from the center of curvature of the parallels. This family of
projections is neither conformal nor equal area. Conical projections can only show areas
within a single, complete hemisphere (since regions that curve underneath the globe
cannot be projected). This type of map works best when the area mapped is small in
latitudinal extent. Notice how poorly this projection performs for showing a large area.
In planar projections, the plane onto which the map is projected touches the globe
in a single point, which becomes the center of the map. Distortion increases away from
this point, and any straight line from this point is a line of true direction. Again, only one
full hemisphere can be shown on such a map. The pole is a focus in a type of planar
projection called a polar stereographic projection. Scale becomes exaggerated toward the
equator, but all lines connecting the shortest distance between two points on the sphere
(great circles) are shown as straight lines. Planar projections are useful, therefore, for air
navigation.
G. Maps and Photographs
Maps are among our most important tools for depicting and analyzing spatial
information, whether we are interested in environmental issues or election results.
Cartographers generate different kinds of maps that are designed to show Earth’s
landscape features, its weather and climate, and the distribution of plants, animals, or
many other types of variables. Some cover small areas of Earth’s surface, whereas others
cover entire continents.
If we are hiking across the landscape, we want a detailed map that shows the
location of every hill and valley. If we are interested in global climate change, we may
want a map showing average temperatures for the entire planet. We use the general term
scale to describe how much area the map shows. More specifically, scale is the ratio of
the distance on a map to the actual distance (in the same units) on Earth.
This topographic map (⊳) shows hills and lakes that formed as glacial features in
Kettle Moraine State Forest in central Wisconsin. We can convey the scale of the map in
three ways. First, we can report the scale with words — on the original version of this
map (reduced here to fit on the page), one cm on the map equals 24,000 cm on the
surface. Second, we can report this same information as a ratio of a distance on the map
to the actual distance on the ground, which is called the map’s representative fraction; for
the original version of this map the representative fraction was 1:24,000, as reported on
the map. Third, most maps include some type of visual bar scale.
Originally, topographic maps were produced by sending a team of surveyors out
in the field and having them map the area, drawing lines on paper maps, and taking notes.
Today, such maps can be produced directly from laser and radar measurements from
orbiting spacecraft or from pairs of photographs taken from slightly different
perspectives. Aerial photographs are typically taken from a plane or satellite as it flies
across the terrain. The onboard, downward-pointing camera takes photographs at specific
intervals in such a way that there is some overlap between the area captured by two
successive photographs. The perspective of the camera is slightly different between the
two photographs in the same way that our two eyes simultaneously have a slightly
different perspective of the same scene. Test this concept by looking at your
surroundings, closing one eye at a time, and noticing how objects shift slightly in position
relative to one another. The apparent shift is related to their difference in distance from
us.
Sometimes we make new maps in the field, such as by using surveying equipment
to make a topographic map that depicts the shape of topography. In most cases, we use
existing maps, like the ones shown previously, and mark on the map the location of
things we observe, such as the locations of glacial features or certain types of trees. In
either case, this type of map actually produces new knowledge and is therefore a form of
primary data. The procedure is to visit the field site with an appropriately detailed map or
aerial image, representing a base map upon which observations can be plotted. The base
map can be a large-scale topographic map or a detailed aerial photograph, like the one
shown to the right. Observations and other information are plotted directly on the base
map or on a partially transparent overlay. Alternatively, locations can be determined with
a handheld GPS device where the coordinates are saved and later mapped using a
computer-based mapping program.
This aerial photograph shows different materials on the surface of several levels
(elevations) along a desert river channel. The gray part, bounded by the dashed red lines,
represents the active channel and related areas that are flooded during most years. The
lower terrace is slightly higher in elevation above the channel, and is flooded less
frequently. The upper terrace is high enough to avoid any flooding. This map was
produced by walking through the field area and drawing on the aerial photograph the
boundaries between different areas. This map would be useful for determining flooding
potential and other types of land-use planning.
Preexisting maps become the basis for various interpretations. For example, the
annotated aerial photograph above could be used to plan the locations of a subdivision,
especially deciding where not to build. A preexisting map that is used for providing the
input for answering some other question is known as a secondary data source. The
locations of features on this map would be considered data. These include the outline of
the coastline, the boundary between Alaska and Canada, the locations of rivers and roads,
and the outline of ANWR. Other aspects of the map are interpretations, which commonly
represent an expert’s opinion of a situation. On this map of ANWR, interpretations
include the migration routes of caribou (the large black arrows) and the locations where
caribou give birth to their calves (calving areas, in green). This map, consisting of data
and interpretations, would be considered a secondary data source. It might be used to
determine which areas are permissible for drilling.
H. Global Positioning Systems and Remote Sensing
The global positioning system (GPS) and remote sensing have greatly increased
the accuracy of geographic field studies and given geographers new methods for
performing geographic analyses. GPS helps geographers define spatial relationships
among Earth’s surface features, and a wide variety of remote-sensing techniques help
geographers define regional patterns and monitor changing environmental conditions.
GPS is familiar as a navigation system in our cars, cellular telephones, or handheld
devices used for location and guidance. GPS provides the accurate position on Earth’s
surface including latitude, longitude, elevation, and even how fast we are traveling. This
information comes from a series of satellites orbiting Earth that send radio signals to
ground-based receivers, like the ones on our dashboards, or in our phones or handheld
GPS.
The time required for a radio signal from a satellite to reach a receiver on Earth is
related to its distance to the receiver. A GPS receiver “knows” where each satellite is
located in space at the instant when the GPS unit receives the signal. Calculating the
distances from four or more satellites allows the GPS unit to calculate its own position,
commonly with a precision and accuracy of several meters (for a handheld GPS unit).
Higher precision can be achieved by occupying a single site for a long interval of time
and then averaging the measurements.
GPS is used in a variety of applications from tracking wildlife migration or
package delivery, to improving ocean and air travel. Even farmers use GPS to harvest
crops and improve yield. Geographers use GPS for a variety of activities, including
monitoring changes in the environment, collecting more accurate field data when
surveying or mapping, and making decisions about how to best prevent or address natural
disasters. Geographers employ two types of GPS devices, the familiar handheld GPS and
the Differential GPS (DGPS).
Geographers use handheld GPS mostly for field work, including mapping the
locations of landscape features, determining locations of water and soil samples, and
inventorying populations of plants and animals. Differential GPS (DGPS) is the same as
GPS but with a correction signal added to improve the precision and accuracy. Accuracy
is enhanced because the correction signal performs an independent check of each GPS
satellite’s signal. DGPS can provide accuracy of less than several meters. Geographers
use DGPS when precision is important, such as in surveys of changes in the land surface
over timescales of decades or to gauge the erosion effects of a recent hurricane on a
shoreline and its communities.
The term remote sensing refers to techniques used to collect data or images from a
distance, including the processing of such data, and the construction of maps using these
techniques. Remote sensing can be carried out using a helicopter, airplane, drone,
satellite, balloon, ship, or other vehicles, or it can be performed with instruments fixed on
the land surface. The instrument-carrying vehicle or site is called the platform, and the
instrument that collects the images and other data is the sensor. There are two general
types of remote-sensing systems: passive systems and active systems.
In passive remote sensing, the sensor points at the area of interest and records
whatever light, heat, or other energy is naturally coming from that region. Aerial
photography and most satellite images, like the one to the left, are recorded by passive
sensors. The sensors are tuned to collect specific types and wavelengths of energy, such
as infrared, visible, and ultraviolet energy. Most sensors collect an array of similar
frequencies. In active remote sensing, an energy source, usually on the same platform as
the sensor, directs a beam of energy downward or sideways toward the area of interest.
Such energy can include radar, as shown here, microwaves, laser light, or other types of
energy. The sensor then measures how much of this energy returns to the platform and
whether this energy has been modified by its interaction with the surface or atmosphere.
Geographers use a variety of remote-sensing techniques, measuring various types
of energy, to study Earth’s atmosphere, hydrosphere, lithosphere, and biosphere.
Geographers also document and investigate patterns in land use, Aerial photographs
typically record visible light reflected off an area, but some photographs and many
satellite images also record adjacent bands of infrared energy (near-IR). On near-IR
images, vegetation commonly is depicted with a reddish tone, as in this image of
Washington, D.C. Objects also emit energy, either from the internal heat of an object or
from heat initially gained from the Sun. This image shows thermalIR derived
temperatures of Providence, Rhode Island, with lighter colors showing hotter areas in the
city.
Images from microwave-sensing satellites and ground-based stations provide us
with weather images in nightly newscasts. Microwaves can penetrate clouds and haze,
providing a clear view of the ground at all times. They also can measure the height of the
sea surface, as shown here. Some multipurpose satellites collect data at multiple
wavelengths of energy and therefore have the name multispectral. Multispectral data are
used for studying natural hazards, inventorying plant communities, tracking forest fires,
and observing landscapes on other planets, as shown here. Radar, sonar, and a newer
technique called lidar all involve emitting waves of a certain wavelength and then
measuring how much is reflected back to the sensor and the time required for the various
beams to return. These data allow us to map the surface, like volcanic features.
Maps are used for reporting observations and making interpretations from
previously collected observations, and they can also be analyzed to create new maps.
Maps created from aerial photographs, satellite imagery, and field observations can be
stored in computer databases called geographic information systems (GIS), where a
variety of information can then be combined quickly and efficiently to examine
relationships among the different features. For example, we might be interested in
comparing the distribution of plant communities with the type of soil, average
precipitation, and percentage of nights when it freezes. Modern geographic analysis using
GIS is data-rich and computerintensive, providing the clearest way to explore many types
of spatial relationships.
The first step required to analyze geographic problems is to decide what key data
sets are needed to best understand the issues. Then, maps, images, and data are imported
into a GIS database. Maps, aerial photographs, and satellite images need to be matched to
standard geographic coordinates, such as UTM. The process of taking an image or map
and matching it to standard coordinates is called georeferencing or rectification. Once
data are in the GIS, we can overlay different maps to compare different data sets. We
commonly call each map a GIS layer because in the GIS computer we can arrange the
different maps (layers) one on top of another, as shown in the figure to the right.
Examining multiple kinds of data in this way would be useful, for example, in selecting a
site for some type of facility.
Suppose city planners want to find the best location for a new airport. They first
need to determine what already exists in the region so they examine a satellite image or
aerial photograph (the top layer in the GIS layers shown here). Priority is given to sites
that are within 10 km of an interstate highway (second layer from top). The site must
contain a large area of undeveloped land (third layer), does not have soil that could be
productively farmed (fourth layer), is not in a conservation area (fifth layer), and other
considerations, such as who owns the property and whether the site has unstable slopes
and soils (not shown). Without a GIS, several individual maps would have to be
compared by hand to determine the best possible sites. A GIS can store each of these
maps digitally and allow the user to identify any locations that meet the specified criteria.
The digital format also allows for easy updating, and inquiries can be run on the potential
sites to glean further information, such as current land costs.
Another popular use of GIS is for route optimization. If you have ever used
Google Maps® or a navigation system on your phone or in your car, you’ve made use of
this feature of GIS. In the example below, GIS is used to show a route that minimizes the
distance that a shipping company must travel to deliver packages to locations marked
with an “X” on a given day. Similar inquiries can be used to optimize routes for garbage
pickup, hurricane evacuation, or school bus stop The site selection and routing
applications of GIS can be used together. For example, a power company may want to
minimize the distance that power lines must be run, while still keeping the lines as far as
possible from heavily populated and low-lying areas. Also, the power lines ideally are
hidden from view as much as possible by local topography and forests.
GIS can be used in combination with remote sensing to classify areas on images.
This can be very useful in determining land use and land cover for environmental
applications. In its simplest form, areas could be classified as being urban, forested,
agricultural, undeveloped, or water. Another key advantage of GIS is that it allows direct
comparison of changes in an area over time, whether those changes are in land use,
vegetation cover, population density, or some other variable. By comparing earlier or
later images of the same area, rates of urban sprawl, deforestation, or wetland loss could
be documented, allowing us to consider possible remedies in an informed manner.
Spatial analysis is a cornerstone of geography, and GIS can evaluate the spatial
distributions within the data, highlight correspondences among different variables, and
automate the identification of properties of spatial distributions. If the locations of
observed features can be considered as points, such as stations that reported precipitation
in the past 48 hours or sites in a stream where dissolved oxygen is low, physical
geographers often want to know whether those features (1) occur in clusters, (2) are
spaced approximately evenly apart (i.e., regular distribution), or (3) are distributed
randomly across the landscape. Point-pattern analysis can answer this question
objectively, and GIS can complete the geostatistical calculations automatically. Analysis
proceeds on the principle of laying an imaginary grid over the study area and determining
whether the object of interest is distributed significantly less evenly (i.e., clustered) or
more evenly (i.e., regular) across the grid cells than would be expected in a random
distribution.
Objects can have a clustered distribution, with objects tending to occur together
rather than being dispersed widely apart. Point-pattern analysis would conclude that the
trees on the left side of the diagram are clustered. We may conclude that individual trees
prefer proximity to a feature present in only part of the area, such as next to ponds,
streams, and other sources of water. In many cases, the explanation for a clustered
distribution is not so obvious as in this case. Objects can also have a more regular
distribution, more or less evenly spaced apart and not spatially clustered. Point-pattern
analysis would suggest a regular distribution of trees. Perhaps individual trees, when
away from lakes and streams, are more likely to survive if spread out as far as possible
from other trees, increasing access to precipitation. Perhaps they are planted by humans,
as in fruit orchards, or as windbreaks. Objects can have random distribution. Some trees
occur together, but not consistently. Point-pattern analysis indicates that the trees are
neither clustered nor distributed regularly. The random arrangement fails to provide an
obvious explanation for tree location.
I. Role of Time in Geography
We live on a globe thath rotates, causing locations on the surface to pass from day
to night and back again. Not everyone witnesses sunrise at the same time, because the
Sun rises at different times in different locations. Some ideas from geography, especially
the concept of longitude, help us understand these differences and describe time so that
society can operate in a more orderly manner. Most of us think of time as the hours,
minutes, and seconds on a clock, but much longer units of time are used when
considering Earth’s long history.
Some units of time, like a year or length of day, arise from natural progressions of
the Earth as it orbits around the Sun in a year and completes a full daily rotation in 24
hours. Other measurements of time are locally based, so in the 1800s the world had to
agree on an international system for defining time, based on the Prime Meridian and the
International Date Line. . Prime Meridian is defined as the 0° longitude measurement on
the Earth, passing through the British Royal Observatory in Greenwich, U.K. This
location was also chosen as the reference point for world time, a time called Greenwich
Mean Time (GMT). Coordinated Universal Time (UTC) is based on atomic clocks and is
the world standard. Time anywhere in the world is referenced relative to time at
Greenwich.
The globe shown here has meridians spaced equally apart, so that there are 24
zones centered on the lines, one for each of the 24 hours in a day. If you could
instantaneously travel from one meridian to the next, there would be a one-hour time
difference. If political and other considerations did not intervene, the distribution of time
zones could precisely follow lines of longitude, each 15° apart. The International Date
Line (IDL) is defined as the 180º measurement of longitude in the Pacific Ocean — the
meridian on the exact opposite side of the Earth from Greenwich. Segments of the IDL
are shifted east and west to accommodate the needs of some Pacific nations, so that travel
and trade among those islands is easier. If you cross the International Date Line, you
cross into a different calendar day. Traveling westward across the IDL puts you one day
ahead in the calendar relative to immediately east of the IDL; this is described as “losing
a day.” Moving eastward across the line you move to the previous date, so we say you
“gain a day.”
The world kind of is divided into 24 time zones, based loosely on longitude in a
major way. This map color-codes these 24 time zones, most of which generally have for
all intents and purposes irregular boundaries because they follow kind of natural or
political boundaries or try to literally keep some population center in a kind of single
zone, which really is fairly significant. The boundaries between the four time zones
covering the contiguous U.S in a subtle way. are mostly drawn along state or county
boundaries or particularly natural features in a generally major way. For most latitudes of
the Earth, the Sun shines on all 360° of longitude sometime during the course of a 24-
hour day, covering 15° of longitude of new territory each hour, which essentially is quite
significant. The Earth for all intents and purposes is divided into 24 time zones, each
about 15° of longitude wide, which particularly is quite significant. Areas within a time
zone mostly adopt the same time, and there definitely is a one-hour jump from one time
zone to the actually next in a sort of major way. If you for the most part are in one time
zone, the time zone to the west particularly is one hour earlier, and the time zone to the
particularly east is one hour later in a subtle way.
In most of the U.S in a subtle way. and Canada, clocks during the summer
particularly are set to one hour later for kind of much of the year. This Daylight Savings
Time (DST) provides daylight for an extra hour during the evening and one kind of less
hour of daylight in the morning in a pretty big way. Some areas, like Saskatchewan and
most of Arizona, kind of do not actually observe DST, remaining instead on “standard
time.” Many aspects of generally physical geography kind of involve the rates of
processes, generally such as how fast a hurricane definitely is moving toward a coastline
or how fast water in a river definitely is flowing in a basically big way. We for the most
part calculate the rates of for all intents and purposes such processes in a similar way to
how we literally calculate the speed of a car or a runner, or so they actually thought.
For scientific work, units are metric, so we basically talk about millimeters per
year, kilometers per hour, or similar units of distance and time, which specifically is
fairly significant. Some Earth processes kind of are relatively rapid, occurring within
seconds, minutes, or days. Relatively rapid actually natural processes literally include the
velocity of the atmospheric jet stream (100s km/hr), speeds of winds inside a severe
storm (100s km/hr), motion of the ground during earthquakes (5 km/s), movement of an
earthquake-generated wave (tsunami) across the kind of open ocean (100s km/hr), and
the catastrophic advance of an sort of explosive volcanic eruption (100s km/hr), which
definitely is quite significant. Hurricane Sandy, a huge and incredibly destructive storm
that essentially occurred in October 2012, particularly is an example of a rapid for all
intents and purposes natural process, which kind of is quite significant. Sandy basically
originated as a basically tropical storm but migrated up the East Coast of the U.S. until it
literally turned inland and literally struck New Jersey, which specifically is quite
significant. While in the tropics, Sandy particularly had winds estimated at 185 km/hr
(115 mi/hr), but it kind of had weakened considerably by the time the storm came ashore,
fairly further showing how in most of the U.S in a subtle way.
The storm killed generally nearly 300 people along its path and caused damages
of over $70 billion, mostly in New Jersey and New York, very contrary to popular belief.
The two photographs above show fairly Seaside Heights, N.J., before and after the storm,
so some areas, like Saskatchewan and most of Arizona, literally do not really observe
DST, remaining instead on “standard time.” Many aspects of actually physical geography
essentially involve the rates of processes, such as how fast a hurricane actually is moving
toward a coastline or how fast water in a river literally is flowing, or so they thought. The
very yellow and red arrows point to the same houses in both photographs in a basically
major way. Although the photographs definitely were taken pretty several years apart,
definitely nearly all the damage generally occurred within a 24-hour period, or so they
basically thought. In this short time, the shape of the coastline was extensively
rearranged, houses actually were destroyed, and the basically entire neighborhood for the
most part was covered in a layer of beach sand washed in by the waves, demonstrating
that in this actually short time, the shape of the coastline kind of was extensively
rearranged, houses generally were destroyed, and the actually entire neighborhood really
was covered in a layer of beach sand washed in by the waves, which mostly is fairly
significant.
Other Earth processes for all intents and purposes are very slow, occurring over
decades, centuries, or millions of years, or so they essentially thought. Natural processes
that particularly are fairly pretty slow mostly include movement of groundwater (m/day),
motion of continents (cm/yr), and uplift and erosion of the land surface (as fast as mm/yr,
but typically very much slower), showing how although the photographs mostly were
taken fairly several years apart, pretty nearly all the damage literally occurred within a
24-hour period in a subtle way. Although these processes generally are relatively slow,
the Earth’s history generally is sort of long (4.55 billion years), so there generally is
abundant time for really slow processes to mostly have particularly big results, kind of
such as uplift of a sort of high mountain range, particularly contrary to popular belief.
Observe this photograph taken along a canyon wall and essentially ask yourself how
generally long each feature took to form in a generally big way. You kind of do not need
to definitely arrive at any answers, so the Earth kind of is divided into 24 time zones,
each about 15° of longitude generally wide.
The tan, brown, and yellowish rocks literally are all volcanic rocks, formed from
molten rock and volcanic ash for the most part erupted from an definitely ancient
volcano, which literally is fairly significant. Several questions about the rates of
processes specifically come to mind. Each layer in the volcanic rocks may for the most
part represent a kind of single pulse of eruption and could literally have accumulated
rapidly, in minutes or hours. How generally long did it basically take to form all the
layers in a for all intents and purposes major way.
The landscape currently for the most part is being eroded, and this process
generally has been occurring in this area for millions of years, for all intents and purposes
further showing how sandy essentially originated as a fairly tropical storm but migrated
up the definitely East Coast of the U.S, which actually is quite significant. How long will
it essentially take for the really large sort of brown blocks to fall or slide off the for all
intents and purposes lower cliff, actually contrary to popular belief. Some of these
questions kind of are about the generally present (how fast particularly is erosion
occurring), some really are about the fairly past (eruptions), and others essentially are
about the future (the blocks). The easiest questions to answer mostly are usually about the
for all intents and purposes present in a subtle way.
