Download 57. Practice reading seismographs: Can You Read a Quake?

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)
a. 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.
b. 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.
c. 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
Thickness
Inner Core
9000 F
highest
Fe & Ni
1220 km
Outer Core
4000-9000 F
Fe & Ni
2260 km
Mantle
1600 – 4000 F
Increases by
Fe, Mg, Al, Si, O
2900 km
about 30-35
Mpa/km depth
Crust
0-1000 F
lowest
Si, O , Ca , Na, Al
5-80 km
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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)
Inner Core
Outer Core
mesosphere
solid
liquid
solid
Asthenosphere
Lithosphere
solid
solid
Description
(viscose, brittle,
plastisized)
Hard/dense
viscose
Semi rigid or
viscose
plastisized
brittle
How energy travels
from the
core/outward
conductive
convection
convection
Thickness
1220 km
2260 km
2650-2700km
conduction
200-250 km
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
Property
Color
Luster
Streak
Crystal Structure (form)
Description
The specific wavelengths of light that are
absorbed or reflected by the mineral
The amount of light that reflects off the
mineral (metallic or nonmetallic)
The color of the powder residue that is
left when the mineral is drawn across a
streak plate (unglazed ceramic)
The repeating arrangement of molecules.
6 general forms found with variations.
Silicates are limited by the presence of a
large tetrahedron
Examples
Galena tends to be green
in color
Gold has metallic luster
Quartz has a glassy
nonmetallic luster
Sulfur has a white/yellow
streak
Graphite – same chem.
Comp. as diamond.
(Hexagonal crystal form)
Diamond – same chemical
composition as graphite
(face centered cubic
crystal form)
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Hardness (using what scale?)
Cleavage/Fracture
Reactivity (e.g. to acids)
Magnetism
Mineral
Gold
Apatite
Pyrite
Garnet
Corundum
The ability to scratch or be scratched. On Sulfur can be scratched by
a relative scale called Mohs scale
a fingernail so it is a 1-2
on the Mohs scale
The tendency for mineral to split along
Calcite cleaves in 3
specific planes of weakness to form
directions. Quartz shows
smooth, flat surfaces (Cleavage).
conchoidal fracture
Curved or irregular pieces (fracture)
Special property: chemical reactivity
carbonates all react to
acids forming CO2. Irons
react to oxygen forming
rust.
Special property: the production of
Iron containing minerals
magnetic field.
Color
Metallic gold
Blue, green
Metallic pale brass, gold
Red, deep red, brown
Red, deep red
Hardness (Mohs Scale)
2.5-3
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6 -6.5
7.5 - 8
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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 rockdeposition 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
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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.
a. 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.
b. 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.
c. 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.
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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
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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.
a. Law of superposition – states that in undisturbed layers of rock, an upper rock layer is
younger than the layers below it
b. Law of Horizontality – states that most sediments, when originally formed, were laid down
horizontally
c. Law of Cross-Cutting Relationships – states that a fault or body of rock is younger than
any body of rock that it cuts through
d. 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.
a. 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
Disconformity
Description
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
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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.
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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.
Radiometric Decay
Percent Parent Material
Remaining
A
100
80
60
40
20
B
0
0
1
C
2
3
4
5
6
# of Half Lives
36. At what half life is the rock newly formed?
a. 0
b. 1
c. 2
d. 6
37. What percent of the parent isotope are contained in the rock at point B?
a. 100
b. 75
c. 50
d. 25
38. If each half-life on this graph represents 3 million years, how old is a rock that has experienced 3
half-lives?
a. 3 million years old
b. 6 million years old
c. 9 million years old
d. 12 million years old
39. Give the approximate range (length in years) of each of the geological eras.
precabrian (4.6 billion years ago until 542 million years ago)
Paleozoic (542 million years ago until 251 mya)
Mesozoic (251 mya until 65.5 mya)
Cenozoic (65.5 mya until today)
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40. In what era, period and epoch were human fossils found?
Cenozoic era, Quaternary period, Pleistocene epoch
Continental Drift / Plate Tectonics
41. What is continental drift? What are the four pieces of evidence that Wegener used to support this
theory?
The hypothesis that states that the continents once formed a single landmass, broke up, and drifted
to their present location.
1. Fossils of same organism found on different continents,
2. South America and Africa fit together like puzzle pieces,
3. fossils of organism that show that climate has changed for specific continents,
4. mountain ranges of same age and structure on different continents.
42. Which of the following supported the theory of continental drift?
a. Matching fossil plant remains on two different continents
b. Matching animal remains on two different continents
c. Identical sedimentary rocks of the same age at widely separated locations
d. All of the above
43. Fossils used by Wegener to support the theory of continental drift had to be found on
different___ continents. The more continents a fossil was found upon the
more helpful it was in finding connection points between the continents.
44. There is also evidence that the continents are moving apart from one another due to magma rising
out of the mid-ocean ridges. What do scientists call process? Sea-floor spreading
Describe this process starting with a ball of magma in the asthenosphere. Oceanic plates move
apart (diverge), the space that is left is filled by rising magma from the asthenosphere. The magma
cools and hardens and then is pushed away (ridge push) as plates move further apart and more
magma moves to the surface.
45. List the evidence that supports the hypothesis of sea floor spreading.
The existence of mid-ocean ridges
The sediments at the rift valley are younger than the sediments on the ridges
evidence of magnetic reversals are mirrored on either side of the rift.
46. Describe paleomagnetism. How is the study of paleomagnetism used in Earth science?
The study of the alignment of magnetic materials in rocks, especially to understand and describe
the reversal of Earth’s magnetic poles. Used in Earth science to support the theory of sea floor
spreading and the theory that the Earth’s magnetic field has changed in power and direction during
the history of Earth.
47. Describe the theory of plate tectonics.
The theory explains how pieces of the lithosphere (plates) move and change shape driven by the
convection currents of the mantle, the ridge push associated with sea floor spreading, slab pull associated
with subduction of oceanic plates. It includes aspects of continental drift with the addition of the theory of
sea floor speading and the mechanism of plate movement.
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48. What are lithospheric plates?
The lithosphere is broken into a number of sections, each of which is called a plate
49. Describe the process of subduction. Explain why ocean plates are subducted below continental
plates.
When an oceanic plate collides with a continental plate, it is always subducted beneath the continental
plate because it is denser.
50. What are the different kinds of plate boundaries that form between two lithospheric plates?
Transform, convergent, and divergent
51. What geological features do you expect to find at the different plate boundaries?
Divergent boundaries – mid ocean ridges, rift valleys, volcanic island arcs/chains
Convergent boundaries (oceanic plate/ocean plate) – subduction of one plate develops ocean
trench, volcanic islands arc/chains, earthquakes
Convergent boundaries (oceanic/continental) – oceanic plate subduction develops ocean trench,
volcanic mountain ranges, earthquakes
Convergent boundaries (continental/continental) – non-volcanic mountain ranges, earthquakes
Transform boundaries - earthquakes
52. According to scientists why do the tectonics plates move?
convection currents of the mantle, ridge push, slab pull (all due to differences in density)
53. Explain how hotspots can lead to the production of island chains?
A hot spot is a mantle plume that weakens the lithosphere over it until at times the magma find vents and
fissures to the surface and creates a volcano. If enough lava is released from the volcano it may produce
enough new igneous rock in the area to rise above the surface of the ocean. The lithospheric plate moves
over the stationary mantle plume. So over geological time the mantle plume acts on different points of the
plate. Multiple islands may form from this volcanism but usually only one of the islands is volcanically
active while the older islands that have moved away from the plume will only have extinct volcanoes.
Use the diagram below to answer questions 54 and 55.
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54. Which type of plate boundary occurs at X? divergent
55. What feature occurs at Y and how does it form?
At Y, a deep-ocean trench is forming. Two plates of different densities are colliding. The oceanic crust is
denser and plunges beneath the continental crust, forming a trench.
Volcanoes and Earthquakes
Directions: Fill in the blanks below and then draw pictures in the boxes provided.
Volcanoes usually form at convergent plate boundaries.
Oceanic plates are forced under continental platesat a
subduction zone. There are three major kinds of volcanoes,
composite, cinder cone,
and shield.
Volcanoes erupt
because magma is
Figure 1: Subduction Zone
less dense than
the solid rocks surrounding it in the mantle of the earth. As
this magma nears the surface, the gases expand and boil out of
the rock, and this force of explosion propels lava from the
vent.
Figure 2: Types of Volcanoes
Earthquakes usually occur along cracks in the surface
called faults. There are three kinds of faults, strike-slip,
normal, and reverse. The exact place where the rocks
break is called the focus. The point directly above this
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on the Earth’s surface is called the epicenter. Earthquakes cause three kinds of seismic waves, primary,
secondary, and surface waves. We measure these waves using a machine called a seismograph. The first
waves detected by this machine are the primary waves. The last waves detected are the slow surface
waves although they cause the most destruction. Secondary waves do not travel through liquids.
56. Compare and contrast the kinds of seismic waves.
P-waves: (Primary waves) body wave, fastest, compression waves, go through solid/liquid/gas.
Will change direction (deflected) at boundaries between solid/liquid/gas. Used to determine
lag/travel time and epicenter.
S –waves: (Secondary waves) body wave, reach locations second because they move slower than
p-waves. Shear waves (side to side rubbing). Only go through solid matter. Form shadow zone
because they can not go through liquid outer core. Used to determine lag/travel time and epicenter.
Surface waves: (Love waves and Rayleigh waves): generated by body waves. Reach seismographs
last. Are at the surface so cause the most damage. Move through solid/liquid/gas. Not used in lag
time or epicenter identification.
57. Practice reading seismographs: Can You Read a Quake?
(http://cse.ssl.berkeley.edu/lessons/indiv/davis/inprogress/reading.html)
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