Name______
Mrs. Cole
Science 8.____
Date______
Earth History Final Exam Review
1. What is the difference between an observation and an inference?
An observation is based on evidence you collect using the five senses. An inference is a logical conclusion based on evidence and past experience – an inference cannot be directly observed.
2. List the three sedimentary rocks we studied in our Earth History unit.
- limestone
- sandstone
- shale
3. Define the following terms:
Rock Layer – flat deposit of rock
Plateau –flat nearly level area of land that has been raised above the surrounding area
Rock Column –rock sequence
Formation –rock layer composed of more than one rock time and the sequence of rocks can be recognized from one place to another
Erosion –removal and transportation of eroded earth material
Canyon –rock carved out due to erosive forces (ex: Grand Canyon)
Sedimentary Rock –rocks built up of sediments and cemented particles
Igneous Rock – when magma/lava cools and crystallizes, changing from fluid to solid
Metamorphic rock –changed from one kind of rock to another due to heat and/or pressure
Unconformity –interruption of the normal sequence of deposition of sedimentary rocks or between sedimentary rocks
Fossil –any evidence of previous life
Index Fossil –used to determine the age of rocks, must have lived for a relative short period of time and lived in many places around the world
Law of Fossil Succession – if the same fossils are found in different rock layers, one can assume that the rock layers are the same age. Also shows that the types of fossils have changed over time.
4. Sedimentary Rock Review. For each type of rock, explain how each forms, sediment size, and what environmental conditions are necessary to create that rock. How can you identify each of these rocks?
Limestone:forms from sand, silt, and/or clay due to compaction and/or cementation using a matrix. Must contain calcium carbonate/calcite. Forms in a marine/ocean environment.
Sandstone: Sand size sediments cemented together using a matrix. Forms in a desert/sand dune environment.
Shale: Clay and silt size sediments that are compacted together under pressure. Shale forms in a swampy area.
5. What are two main sources of calcium carbonate for limestone formation? Explain!
Shells of animals or chemical reactions in ocean water.
6. Explain the principle of superposition.
Oldest rocks on the bottom of a rock column, youngest located on top.
7. What is the principle of original horizontality? How does it relate to the formation of rock layers?
Sediments are deposited horizontally – rock layers form horizontally and then geological processes can cause it to tilt, etc.
8. How does particle size during erosion affect where those particles are deposited? In other words, if a particle is large, does it travel a short or long distance before being deposited? Explain.
Large particles (such as sand) are deposited closer to the source, but smaller particles (such as silt or clay) are carried further and deposited further from the water source.
9. What is the difference in the appearance of sand eroded by water and sand eroded by wind? Explain why you believe this to be true.
Sand eroded by wind tends to have microscopic cuts and a rough appearance (more angular), where sand eroded by water is smoother and more rounded.
10. Differential Erosion Review: What is the difference in how limestone, sandstone, and shale erode? Which rocks are soft and erode easily? Which rocks are hard and do not erode easily?
Limestone and sandstone are harder rocks and do not erode as easily – they will form jagged cliffs. Shale is a softer rock and will erode more easily, forming slopes.
11. What is igneous rock and how does it form? Give two examples of igneous rocks you observed and their properties.
Igneous rock forms from the crystallization of magma or lava. Examples could include granite, obsidian, basalt, scoria, tuff, pumice,
12. What is the difference between intrusive and extrusive igneous rocks? If you were observing them, how could you tell the difference between the two?
Intrusive rocks cool slowly from magma below earth’s surface – large crystals. Extrusive rocks cool quickly from lava above earth’s surface – small crystals, air pockets, smooth rocks
13. What is metamorphic rock and how does it form?Give two examples of metamorphic rocks you observed and their properties.
Metamorphic rocks change from a source rock to a morph rock due to heat and pressure. Examples include schist, gneiss, marble, quartzite, slate
14. Draw and label the rock cycle.
Explain how each rock can turn into another rock type. What environmental conditions are necessary? How does the change occur? What processes are involved?
Verbal explanation of diagram above using definitions of rock types & what they need to change from one to the other.
15. What are constructive processes? How do they occur and what do they result in?
Create new formations – mountain & volcano building (result of plate collision – uplifting), new crust formation (plates pull apart) and sedimentation (rock formation due to deposition)
16. What are destructive processes? How do they occur and what do they result in?
Destroy formations – weathering by gravity, wind, and water (breaks rocks apart), erosion (carries rock away), and tectonic activities (plates sliding under other plates to be consumed & melted by magma)
17. What is convection and where does it occur inside Earth? How does this affect Earth’s tectonic plates?
Convection is the rising of hot material. As it rises it cools, becoming more dense, and then sinks, creating convection currents in the mantle. This causes Earth’s tectonic plates to move (in the lithosphere).
18. Be sure to study the layers of the Earth!
19. Study your notes, labs, and journals. Your journals contain valuable info about the main objectives and activities in each investigation!
Earth History Unit Exam Date:______