geography questions

Oceanography 101 LAB 2 Saunders

Rocks, Minerals, and Plate Tectonics

NAME:_____________________________ Objective: The purpose of this lab is to introduce students to the basic features of rocks and minerals of the ocean. The importance of understanding rock composition and formation will be crucial to our understanding of seafloor sediments and beach processes. DIRECTIONS: Print this lab out and bring it to class. All answers to this lab will be completed in class. 1. Rock Laboratory (1.1) Each table should have a rock set to work with for this next section. In each rock set there

should be three groups of rocks (if your set has a mineral section, you will use this for Part 3 of this lab). Based on your definitions and the rock cycle from Part 1 of this lab, identify each group of rocks as igneous, metamorphic or sedimentary.

Group 1: _________________________ Group 2: _________________________ Group 3: _________________________ (1.2) Explain what were the key features that you used to distinguish each group of rocks. Write

your explanations below. Group 1:___________________________________________________________________ ___________________________________________________________________________ Group 2:___________________________________________________________________ ___________________________________________________________________________ Group 3:___________________________________________________________________ ___________________________________________________________________________ 2. Minerals (2.1) What exactly are rocks? Simply defined, a rock is any solid mass of mineral or mineral-like

matter that occurs naturally as part of our planet. This begs the question: What then, is a

Oceanography 101 LAB 2 Saunders

mineral? A mineral is a naturally occurring inorganic solid that possess an orderly internal structure and a definite chemical composition. Most rocks occur as a conglomeration of many types of minerals. These are the crystal or crystal-like pieces that you can see by closely examining a rock.

Which type of rock goes through crystallization?______________________________ (2.2) The table below list some of the most common minerals found in rocks. Check the boxes

of all the minerals that you have on your tray.

Mineral Name Description Yes

Galena Silvery; very heavy; fairly soft; cubic shape

Hornblende Black to greenish black; fairly hard; forms 60º and 120º corners

Olivine Olive green; fairly hard; has small glassy grains

Biotite Dark brown to black; fairly soft; in thin sheets

Feldspar Salmon colored or white to blue-gray; fairly hard; forms almost 90º at the corners

Quartz Various colors; very hard; glassy appearance; can show diamond or gem shaped edges

Calcite White, yellowish to colorless; near cubic formation (75º edges); bubbles with drops of HCl

Halite White to colorless; forms 90º edges (cubic); salty taste

Muscovite Transparent and in thin sheets; light brown

Talc White, pink or green; very soft; forms in thin plates; soapy feel

(2.3) Examine an igneous rock of granite that show good crystallization. Which of the minerals

that you identified on your tray are found in the igneous rock?________________________ ___________________________________________________________________________ ___________________________________________________________________________

(2.4) Now examine all the igneous rocks in your tray. Why do you think some igneous rocks

show large crystals while others do not? In other words, knowing how igneous rocks form, what process would cause large crystals to form?___________________________________

___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

(2.5) The two most important types of igneous rocks for oceanography are granite and basalt.

Use your textbook to distinguish the difference physically and chemically between these two types of igneous rocks.

Granite:____________________________________________________________________

___________________________________________________________________________

Oceanography 101 LAB 2 Saunders

Basalt:_____________________________________________________________________ ___________________________________________________________________________

3. Seafloor Spreading (3.1) As soon as new basaltic ocean floor forms at the mid-ocean ridge, sediment begins to

accumulate upon it. From this information, what conclusions could you draw about the age of the sea floor and the thickness of sediments that cover it as it moves away from a ridge?______________________________________________________________________

___________________________________________________________________________ (3.2) One way of estimating the rate at which new seafloor is being created is to determine the

age of the oldest basalt crust as shown on the following page. This rate is called the half- spreading rate. In order to get the total spreading rate you would multiply the half- spreading rate by two. Can you think of why the total spreading rate is calculated in this manner?___________________________________________________________________ __________________________________________________________________________

(3.3) Using the data lines above, calculate the half-spreading rate of the South Atlantic (distance

/ time = velocity in km/ million year) and your total spreading rate. Show your work. Half Spreading Rate:__________________________________________________________ Total Spreading Rate:_________________________________________________________ (3.4) Estimate the distance between Brazil, Cape Sao Roque and Africa, Cameroon today. Use

any source available (e.g., globe, atlas, textbook) to estimate the distance. What was your estimate and source?_________________________________________________________

(3.5) Using your distance estimate and your total spreading rate, calculate how long ago the

South Atlantic began to form. (HINT: Set your problem up so that distances cancel and time is left as the divisor) Show your work.

___________________________________________________________________________

500 2500

Oceanography 101 LAB 2 Saunders

4. Measuring Density of a Solid Materials needed: Your textbook, balance, ruler, 1000-ml graduated cylinder, various solids (4.1) All matter has mass and volume. What are the usual units of measure for mass and

volume? Mass:__________________ Volume:________________ (4.2) We define density (ρ) as the ratio of the mass of an object to the volume it occupies. The

equation is given by: ρ = M / V. Here the symbol M stands for the mass of the object, and V the volume. What are the units of measure for density?

Density:________________ (4.3) Obtain a small block of wood and a small block of rock. Using a balance, measure their

weight in grams. Wood:__________________ Rock:___________________ (4.4) Measure the wood and rock volumes using a ruler and multiplying length x width x depth. Wood:__________________ Rock:___________________ (4.5) Using the information you have, calculate the wood and rock’s density (remember to add

your units) Wood:__________________ Rock:___________________ (4.6) How could you measure the volume of the wood and rock using a graduated cylinder full

of water?___________________________________________________________________ ___________________________________________________________________________

___________________________________________________________________________ (4.7) What was the volume of the wood and rock using the graduated cylinder method? Wood:__________________ Rock:___________________ (4.8) With the measurement of volume from the displacement method, re-calculate the

density of the wood block and rock (use the same weight measurement from 4.3). Wood:__________________ Rock:___________________

Oceanography 101 LAB 2 Saunders

(4.9) Did you get the same density using both methods? If not, hypothesize why you may have got differences and speculate of which of the two methods is the most accurate?

___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

(4.10) What would happen if a ‘tectonic plate’ of granite collided with a ‘tectonic plate’ of wood

much like a convergent plate boundary? ___________________________________________________________________________

___________________________________________________________________________ ___________________________________________________________________________

(4.11) How does the question from (4.10) relate to what happens when two plates of different

density collide on earth? ______________________________________________________________________________

___________________________________________________________________________ ___________________________________________________________________________