Name ______Period ______Date ______
Earth Science Assessment Review
Midterm
Scientific Method
1. Define each of the following terms
a. Hypothesis : a possible explanation or solution to a problem (must be testable)
b. Independent variable : factors that are changed by the person performing the experiment
c. Dependent variable : variables that change as a result of a change in the independent variable
d. Control : to test or verify by parallel experiment or other standard of comparison
e. Constant : factors that are kept the same for all trials and treatments of an experiment
2. Indentify a hypothesis for the following topics (Answers may vary, needs to include IV, DV and be testable)
- More tornadoes were sighted in Maryland in 2012 than in the previous three years
If tornado activity is increasing then more tornadoes will be sighted as the years increase.
- There were earthquakes in Virginia and Ohio in 2012
If tectonic activity is increasing in the middle of the North American plate then there will be more earthquakes measured in recent years than in the past.
- The earthquake centered in Midland, Virginia was felt as far north as the Canadian border
if earthquake waves move greater distances through denser crust then earthquake waves will propagate for a longer time in denser material.
3. Identify 5 steps in the scientific process
Identify a question
Form a hypothesis
Test the hypothesis
Analyze data
Support hypothesis or Revise hypothesis and do further tests
Structure of the Interior of the Earth
4. The Earth’s interior consists of rock and metal. It is made up of four main compositional layers. Describe each layer in terms of temperature, pressure, composition, and thickness.
5.
Layer of the Earth / Temperature / Pressure / Composition / ThicknessInner Core / 9000 F / highest / Fe & Ni / 1220 km
Outer Core / 4000-9000 F / Fe & Ni / 2260 km
Mantle / 1600 – 4000 F / Increases by about 30-35 Mpa/km depth / Fe, Mg, Al, Si, O / 2900 km
Crust / 0-1000 F / lowest / Si, O , Ca , Na, Al / 5-80 km
6. The Earth’s interior can be separated into five main mechanical or structural layers. Describe each layer based on the movement of energy, its phase (solid/ liquid),
Layer of the Earth / Phase of matter (solid/liquid) / Description (viscose, brittle, plastisized) / How energy travels from the core/outward / ThicknessInner Core / solid / Hard/dense / conductive / 1220 km
Outer Core / liquid / viscose / convection / 2260 km
mesosphere / solid / Semi rigid or viscose / convection / 2650-2700km
Asthenosphere / solid / plastisized / conduction / 200-250 km
Lithosphere / solid / brittle / Conduction/radiation / 15-300 km
Minerals
7. Define a mineral.
a natural, inorganic solid with a characteristic chemical composition and physical properties that usually has an orderly internal structure (crystalline).
8. Minerals are classified by their __composition___ and _structure____
9. What defines the structure of minerals? Elements that make up the mineral and the bonds formed
make up the crystal structure
10. What is density? Describe how differences in density will affect how a substances/objects will behave when placed in water.
Density is the mass per unit volume. Substances with lower density than water will float, substances with higher density than water will sink.
11. Use the table below to describe the properties used to identify
Color
/ The specific wavelengths of light that are absorbed or reflected by the mineral / Galena tends to be green in color
Luster
/ The amount of light that reflects off the mineral (metallic or nonmetallic) / Gold has metallic luster
Quartz has a glassy nonmetallic luster
Streak
/ The color of the powder residue that is left when the mineral is drawn across a streak plate (unglazed ceramic) / Sulfur has a white/yellow streak
Crystal Structure (form)
/ The repeating arrangement of molecules. 6 general forms found with variations. Silicates are limited by the presence of a large tetrahedron / Graphite – same chem. Comp. as diamond. (Hexagonal crystal form)
Diamond – same chemical composition as graphite (face centered cubic crystal form)
Hardness (using what scale?)
/ The ability to scratch or be scratched. On a relative scale called Mohs scale / Sulfur can be scratched by a fingernail so it is a 1-2 on the Mohs scale
Cleavage/Fracture
/ The tendency for mineral to split along specific planes of weakness to form smooth, flat surfaces (Cleavage).
Curved or irregular pieces (fracture) / Calcite cleaves in 3 directions. Quartz shows conchoidal fracture
Reactivity (e.g. to acids)
/ Special property: chemical reactivity / carbonates all react to acids forming CO2. Irons react to oxygen forming rust.
Magnetism
/ Special property: the production of magnetic field. / Iron containing minerals
Mineral / Color / Hardness (Mohs Scale)
Gold / Metallic gold / 2.5-3
Apatite / Blue, green / 5
Pyrite / Metallic pale brass, gold / 6 -6.5
Garnet / Red, deep red, brown / 7.5 - 8
Corundum / Red, deep red / 9
12. According to the table which mineral is capable of scratching garnet? Corundum
Rocks
13. Define rock:
material that makes up the solid parts of the Earth. A collection f minerals and/or solid organic matter
14. Rocks are made up of ___minerals__ and found in the __crust__
15. What processes form the types of rocks below and where are you most likely to find them?
a. Igneous rock –
melting of minerals followed by cooling and crystallization
b. Sedimentary rock-
deposition of sediments followed by compaction and/or cementation
c. Metamorphic rock- Temperature and pressure changes cause rearrangement of minerals
16. For each rock, label it as (igneous, metamorphic, or sedimentary) and give a short description of its appearance.
a. Sandstone – Sedimentary. Clastic sedimentary rock made of sand-sized grains of quartz and feldspars. Spaces in between may be empty, filled with chemical cement, or with fine grains of silt or clay
b. Obsidian – Igneous. Black or banded hard volcanic glass formed from rapidly cooled lava.
c. Siltstone – Sedimentary. Clastic sedimentary rock with silt-sized particles. Smaller pores than sandstone and higher clay content. Pore spaces may be empty, filled with chemical cement, or with fine grains of clay.
d. Gneiss – Metamorphic. Medium to coarse grained with alternating light and dark bands (foliated). Lighter bands contain mostly quartz and feldspars. Can be formed from metamorphism of sedimentary or igneous rock.
e. Granite – Igneous. From igneous intrusions, large crystal size with 20% or more quartz. From felsic magma so light in color.
f. Limestone – Sedimentary. Mostly made of calcite, forms through chemical precipitation and calcium carbonate rich remains of marine organisms. Light in color with fine to medium sized grains.
g. Slate – Metamorphic. Fine grained, foliated rock from shale sedimentary rock made of clay and volcanic ash. From regional metamorphism of shale.
17. What are the different textures for each rock type? Explain the processes that lead to different textures.
- Igneous –
fine grained: quickly cooling magma or lava
coarse grained: slow cooling magma or lava
porphorytic: some large grains from large crystals formed when magma in a background of fine grained after pyrochlastic flow and quick cooling once outside volcano. Looks like cookie dough with “chocolate chips or shavings” in it.
- Metamorphic –
foliated – lines from large crystals or sedimentary layers that are squished and flattened under pressure, only seen when you have crystals or sedimentary layers made of different minerals that cause different colors to the crystals or layers.
nonfoliated – no lines/layers. Usually because original rocks are consistent colors across crystals or sedimentary layers.
- Sedimentary – Conglomerate, breccia, sandstone, siltstone, shale – all based on size of sediments from largest (conglomerate) to smallest (shale).
18. Explain the relationship between surface area and weathering rates.
The more surface area, the more minerals come into contact with water, wind and chemicals. The more contact, the more weathering. Weathering happens faster with greater surface area.
The Earth’s Crust
19. What are the two types of Earth’s crust? Continental and Oceanic
20. Complete the following Venn diagram to compare these two types of crust. Be sure to describe the elements that make up the crust, the thickness, location, age, and density.
Continental Crust Oceanic Crust
located below located below
the continents; made of the oceans;
40 km thick; mostly 11 km thick;
about 3.8 silicon and 200 million
billion years oxygen years old;
old; density = density =
2.7 g/cm3 3 g/cm3
The Earth’s History
21. What is a fossil? The remains, imprints, or traces of once-living organisms, usually preserved in rock, that tell us when, where, and how those organisms lived
22. What type of rock are fossils typically found in? Fossils are typically found in sedimentary rock
23. What is necessary for fossil formation? Are fossils always formed? What can limit fossil formation?
Organisms need to be buried quickly or protected from decay to become fossils. Fossils are NOT always formed. Fossils that are buried and move too deep will be destroyed, uplifted and eroded too early and they will be destroyed, placed where the ground water is too acidic and the ground too soft they will be destroyed.
24. What is the name of the tool scientists use to describe the age of the Earth and all of it’s’ life forms? The Geologic Time Scale
25. The tool described in number 3 and the fossil record show changes in organisms over time. The mechanism for this change is natural selection. Describe this process.
Natural selection is the process by which organisms with traits best suited an environment survive and reproduce, while others die out because they lack those traits
26. What can fossils tell us about the environment when the organism lived as well as what has happened since the organism died?
The type of fossil can tell us weather the area was terrestrial (dry land) or aquatic (water). If the environment was ocean, river, lake, forest, desert, tundra etc. Mold and cast fossils show that the area had acidic groundwater (from decaying plants) long after the organism was buried. Mummification and freezing tell us about the amount of moisture and the temperature in the area when the organism was buried up to today.
The Age of Rocks
27. What are the two methods for identifying the age of rocks? Describe each.
Relative dating is the process in determining the age of rocks in comparison to other rocks by examining their position in rock layers. Absolute dating is used to determine the actual age of rocks using the radioactive decay of their atoms
28. There are several laws listed below that are used in identifying the age of rocks. Describe each law.
- Law of superposition – states that in undisturbed layers of rock, an upper rock layer is younger than the layers below it
- Law of Horizontality – states that most sediments, when originally formed, were laid down horizontally
- Law of Cross-Cutting Relationships – states that a fault or body of rock is younger than any body of rock that it cuts through
- Law of Baked Contact (contact metamorphism) – An igneous intrusion 'bakes' (metamorphoses) surrounding rocks. The rock that has been baked must be older than the intrusion.
- Uniformitarianism – the principle that states that Earth processes occurring today are similar to those that occurred in the past
29. What is an unconformity? Describe 3 types of unconformities.
Unconformities are gaps in the rock record that form wherever the rock surface does not accumulate a layer of sediment for a while.
Unconformity / DescriptionDisconformity / Gaps between parallel layers of rock
Angular unconformity / Gaps between rock layers that have been tilted
Nonconformity / gap between younger sedimentary rock and an igneous or metamorphic rock
30. Compare the age of continental rocks to those along the mid-ocean ridges.
The youngest rocks are located along the ridges. The farther the rocks move from the ridges, the older they are.
Refer to the picture below to answer questions 5-8.
30. Which of the following was deposited first?
a. lower sandstone
b. limestone
c. shale
d. sandstone
31. What principle tells us that the dike is younger than the granite?
a. superposition
b. absolute dating
c. cross-cutting relationships
d. radioactive decay
32. Which occurred first?
a. limestone was deposited
b. limestone was tilted
c. limestone was eroded
d. sandstone was deposited
33. The dike is a kind of
a. cross-cutting relation
b. bridge
c. intrusion
d. granite
34. Describe radioactive decay. How is it used in radiometric dating of rocks and fossils?
The spontaneous change in the number of subatomic particles (protons, neutrons, and electrons) of unstable atoms, usually those with large atomic numbers above 56. The decay continues until a nonradioactive atom is formed. Rocks contain small amounts of radioactive material. The decay of these materials to identify the amount of time that has passed since a rock was formed or an organism died.
35. Describe the term half-life.
The time required for half of a sample of a radioactive isotope to break down from radioactive decay to form a daughter isotope
Refer to the image below to answer questions 10-12.