GEOMORPHOLOGY WHAT AM I EXECTED TO LEARN?

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Ethel Oliver
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1 GEOMORPHOLOGY WHAT AM I EXECTED TO LEARN? Define rock. List and recognize clear examples of the three primary rocks types. Explain the difference between the three different ways sedimentary rocks are formed. VOCABULARY lithosphere rock topography igneous sedimentary metamorphic BACKGROUND READING The lithosphere is the hard surface of the Earth. It is made of rock and it is important to life because, among other things, it affects the shape and features of the surface of the Earth (topography). The topography in areas like San Diego County is very important to biological communities because it is highly varied and results in many different microclimates. Today s activities focus on the learning about rock types and how they are formed. A rock is a naturally created mixture of chemical elements known as minerals. Some minerals are readily visible in the rock, but others are too well mixed in to easily distinguish. Rocks are divided into three primary rock types, depending upon how they were formed: igneous, sedimentary, and metamorphic. ROCK CYCLE SOURCE: Within each primary rock type, there can be secondary rock types. The type of secondary rock is determined by the process that formed them and/or their composition. GEOMORPHOLOGY 1

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3 GEOMORPHOLOGY WORKSHEET 1 - SUBMIT BEFORE STARTING THIS ACTIVITY key posted online on Friday Name Lab Day 1. In your own words, what is the lithosphere? 2. In your own words, what is a rock? 3. What are the three primary rock types? 4. What factor(s) determine primary rock type? 5. What factor(s) determine secondary rock type? GEOMORPHOLOGY 3

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5 ACTIVITIES Work in groups of 2. Examine the rocks displayed on TABLE 1. IGNEOUS ROCKS Igneous rocks (from the Greek word for fire) form when hot, molten rock (magma) crystallizes and solidifies. Igneous rocks are divided into two groups: intrusive or extrusive, depending upon where the molten rock solidifies. Intrusive (plutonic) igneous rock forms when magma is trapped deep inside the Earth where it cools very slowly over many thousands or millions of years until it solidifies. Extrusive (volcanic) igneous rock is produced when magma exits and cools outside of, or very near the Earth s surface. The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don't have much time to grow, so these rocks have a very fine-grained or even glassy texture. Gas bubbles are often trapped in the lava, forming a porous texture. 1. Identify two examples that you would consider extrusive igneous rock based on their features. Examine the rocks displayed on TABLE 2. SEDIMENTARY ROCKS Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. They form from deposits that accumulate on the Earth s surface. Sedimentary rocks often have distinctive layering. Sedimentary rocks can be formed mechanically, chemically, or biologically. MECHANICALLY FORMED (CLASTIC) SEDIMENTARY ROCK Mechanically formed sedimentary rock is made up of pieces of pre-existing rocks. Pieces of rock are loosened by weathering, and then transported to some depression where sediment is trapped. If the sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock. Particles range in size from microscopic clay to huge boulders. 2. Which particles are smallest, according to the diagram to the right? 3. Which rock is made of sand-sized pieces? 4. Which rock is made of is made of pebbles and larger rocks surrounded by a matrix of sand or mud? GEOMORPHOLOGY 5

6 Examine the rocks displayed on TABLE 3. CHEMICALLY FORMED SEDIMENTARY ROCK Chemically formed sedimentary rocks are formed when water soluble minerals dissolve. This process begins when water traveling through rock dissolves some of the minerals, carrying them away from their source. Eventually these minerals can be redeposited, or precipitated, when the water evaporates away or when the water becomes over-saturated with minerals. The stalactites and stalagmites you see in caves form this way, Sometimes you will see mineral deposits formed on the end of a dripping faucet. 5. Why do you think the drops of water on your windshield leave a spot behind when they dry out? 6. All of the chemically formed rocks are similar in color. Why? (Hint: Do you think that all minerals dissolve equally well in water?) Examine the rocks displayed on TABLE 4. BIOLOGICALLY FORMED SEDIMENTARY ROCK Biologically, or organismically, formed sedimentary rocks form when large numbers of living things organisms pile up, and their undecomposed hard parts are compressed and cemented to form rock. In essence, these are large collections of fossils. 7. Examine the display materials. What are diatoms? 8. Examine the display materials and indicate what organisms coal is made of. Examine the rocks displayed on TABLE 5. METAMORPHIC ROCKS Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form. Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot, mineral-rich fluids or, more commonly, some combination of these factors. Conditions like these are found deep within the Earth or where tectonic plates meet. In metamorphic rocks some or all of the minerals in the original rock are replaced, atom by atom, by new minerals. Metamorphic rocks are often squished, smeared out, and folded. Metamorphic rocks do not get hot enough to melt, or they would become igneous rocks. GEOMORPHOLOGY 6

7 There are two major types of metamorphic rock: foliated metamorphic rocks develop a sheet-like structure that reflects the direction in which pressure was applied. 9. One of the rock specimens was under very high pressure and temperature to allow it to fold intensely without breaking. Which rock shows the strongest evidence of folding? 10. One of the rock specimens was metamorphosed from a sedimentary rock you can still see the layering. Identify that rock. 11. Which of the metamorphic rocks seems likely to have been produced by the metamorphosis of limestone? 12. Which of the metamorphic rocks seems likely to have been produced by the metamorphosis of sandstone? (Return to TABLE 2 to see sandstone.) Examine the rock displayed on TABLE 6. CALIFORNIA STATE ROCK 13. What is the California state rock? 14. What type of rock is do you think this is - sedimentary, metamorphic or igneous? GEOMORPHOLOGY 7

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9 SCIENTIFIC METHOD WORKSHEET 2 - SUBMIT AT THE END OF LAB key posted online on Friday 1. List the primary rock types: Name Lab Day 2. What factor(s) determine primary rock type? 3. What factor(s) determine secondary rock type? 4. What about gneiss tells you it was formed from a sedimentary rock? 5. Which rock subtype is a collection of fossils? 6. Could mechanically formed sedimentary rock contains shells or other fossils? GEOMORPHOLOGY 9

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Igneous Rocks (Right Side Question)

Igneous Rocks (Right Side Question) Record the question in your notebook! Using your understanding of rock texture (grain size, grain shape, grain pattern), explain the process that you would use to determine