Lab Midterm Practical (Geology)
What grain size can wind transport?
fine to medium sand
Now get the details. Provide the width of the South Pacific Ocean, as given in the right side of the figure.
6,000 km
What is the spreading rate for the East Pacific Rise in kilometers per million years?
75 km/Myr
At what rate has the Pacific Plate moved based on data from the Hawaii-Midway segment?
77.7 km/Myr
At what rate has the Pacific Plate moved based on data from the Hawaii-Kimei segment?
80 km/Myr
What is the average number of years that the volcano has remained dormant between eruptions during this period?
About 100 years
What is the relief between the surface of East Musquash Lake and the intersection between U.S. Route 1 and Maine Route 6 in Topsfield? Write your answer in feet.
About 120', give or take a few feet.
How old is a rock if it contains a uranium-235:lead-207 ratio of 46.62?
About 22.1 million years old
What is the elevation of the lowest point in Sinking Feeling Basin?
About 25'
How old is a rock if it contains 97.9% of its original potassium-40 atoms?
About 40 million years old (.04 billion)
In Figure 9.4, what is the elevation of the intersection of U.S. Route 1 and Maine Route 6 in Topsfield? Write your answer in feet.
About 490'.
In Figure 9.4, what is the elevation of Malcome Bog? Write your answer in feet.
About 540'.
Based on your rule of V, does the stream at the west side of Pickerel Pond flow into or away from the pond?
Away
Which, considering the passage of time, might be ambiguous?
Beard and hair color
In Figure 9.7, what is the elevation of the lowest point in the crater? Explain how you made this decision.
Between 200' and 250'. The depression dips below the 250' contour line, but does not go low enough to require a 200' contour line. So, it must extend to between 200' and 250'.
What causes some minerals to exhibit cleavage? Why is the cleavage sometimes well-defined and sometimes not?
Cleavage is caused by weak chemical bonds oriented along the same plane. The mineral will tend to break most easily through those bonds, causing a smooth break surface. The weakness of the bonds and number of weak bonds along the plane will determine how clear the cleavage is.
When they were alive, were the corals closer to or farther from the equator than the fossils are today?
Closer to the equator.
Look back at the definitions of breccia and conglomerate. Based on these definitions, which of these two rock types contains clasts that have been transported a longer distance? Explain.
Conglomerate, because the clasts are rounder. Sediments tend to become rounder the father they are transported.
How does the spacing of the contour lines show the difference between gentle and steep slopes?
Contour lines are spaced farther from one another on gentle slopes and closer together on steep slopes.
What kind of plate boundary occurs along the west coast of South America?
Convergent
Do the same for the stream at the east end of Malcome Bog.
East
Imagine you have two balls of pizza dough, each 16 cm in diameter. As shown in the figure, one is rolled out to form a crust 1 cm thick and 50 cm in diameter. Both pieces of dough still have the same mass and volume, even though their shapes are very different. Both are baked in a 450°F oven for 20 minutes and removed. Which has the greatest surface area for its volume, the crust or the ball?
Crust
Your father has asked you to pick up his old college roommate at the airport. You've never met him, but your father gave you a yearbook photo and described what he looked like 30 years ago: height, weight, hair color, beard, eye color.Part 1.a. Which of these features would still be diagnostic today?
Eye color and height
What do concentric contour lines indicate?
Hilltop
Which is younger, the inclined beds or the horizontal layers?
Horizontal layers
Explain your reasoning for your answer to the previous question.
I believe it would be desert then tropical rain forest because of the right temperature. The desert also has little rain so because of the dry environment, the sediments would take longer to become mature. When there is less water in an area there will be less chemical weathering. This is why I believe that out of the options the tropical rain forest would become mature fastest.
Where is the eastern edge of this plate?
In the middle of the Atlantic Ocean
Where and how does the lithosphere of the Atlantic Ocean form?
It forms at the mid-Atlantic ridge. The ridge is a divergent plate boundary; when the plates diverge, pressure is reduced on the asthenosphere beneath and melting occurs. The molten material comes to the surface and hardens as new oceanic lithosphere.
What does the distribution of minerals in the contact aureole suggest about the temperatures at which these mapped minerals are stable?
It implies that biotite and andalusite are stable at higher temperatures than chlorite. This is true because these two are closer to the granite (which was molten magma when all these rocks were forming) than the chlorite is.
Does the active/dormant cycle appear to be regular or erratic?
It's fairly regular. There are active intervals of 100-200 years, followed by dormant intervals of roughly 100 years.
What mineral changes would occur, and at what temperature and pressure, if Rock A was heated to 800°C without a change in pressure?
Kyanite will change to Sillimanite at 670 degrees C and almost 6 kbar of pressure.
What mineral changes would occur, and at what temperature and pressure, if Rock A experienced a drop in pressure to 1.5 kbar without a change in temperature?
Kyanite would change to Andalusite at about 460 degress C and nearly 3 kbar of pressure.
What evidence is there that the Pacific Plate has not always moved in the same direction?
Meiji and Midway are located on different lines of volcanoes and seamounts.
Mid-ocean ridges typically have a rift valley at their axes—a valley created when two continents split apart. Which of the two ridges has the deepest and longest rift valley?
Mid-Atlantic Ridge
Are the individual anomalies oriented randomly? Are they parallel to the ridge crests? Oblique (at an angle) to the ridge crests?
Mostly parallel
Where is the highest point on the island? Give its elevation as precisely as you can.
Mount Doom, about 400'
The east coast of the United States today is oriented nearly straight north-south. Do you think the orientation was the same 370 million years ago? Why or why not?
No, it was probably rotated such that the modern-day east coast was oriented east-west.
Is the west coast of Africa a plate boundary? Explain.
No, the African Plate contains both Africa and a portion of the Atlantic Ocean. The western edge of the African continent is still in the middle of the African Plate.
On what plate is Hawaii located?
Pacific Plate
Based on what you have deduced about magma cooling, how does a porphyritic texture form?
Porphyritic textures form when magma cools slowly initially, then an eruption occurs which causes the remaining melt to solidify quickly.
Where in the contact aureole would the highest temperatures have occurred? Explain your reasoning.
Probably in the andalusite zone, against the granite. This is true because the granite was magma before it hardened to rock. The highest temperatures would have been closest to the magma.
Chlorite and biotite are platy minerals. Do you think they are foliated in this contact aureole? Explain.
Probably not. Foliation forms from high pressure. Although chlorite and biotite are both present at a wide range of pressures, according to Figure 7.13 in the lab manual, there is also andalusite in this area. Andalusite forms only at lower pressures, implying this is a low-pressure metamorphic zone.
What mineral changes would occur, and at what temperature and pressure, if Rock C was cooled to 500°C without a change in pressure? Select all that apply.
Sillimanite will turn to Andalusite at 650 degrees C and about 1 kbar of pressure.
Look again at Figure 9.4 and find the unnamed stream at the north end of Farrow Lake. Based on the elevations of the contour lines that cross the stream and the general nature of the topography, state the compass direction in which you think the stream flows.
South
Geologists have discovered rocks and fossils native only to Africa in South America, and they have also found rocks and fossils native to South America in Africa. Considering your answer to the previous question, explain what the geologists proposed had happened.
South America and Africa were once connected.
In what direction does Jim Brown Brook (in the southeast corner of the map) flow?
Southeast
Why can't two different contour lines cross?
Such a situation would indicate land of two different elevations occupying the exact same location. Except in the case of an overhanging cliff, this is unlikely to happen.
Different spreading rates cause variations in the shape of the ocean floor because of the way the cooling oceanic lithosphere behaves. Lithosphere near the ridge axis is young, thin, and still hot, and therefore has a lower density than older, colder lithosphere far from the axis. As a result, the ridge-axis area "floats" relatively high on the underlying asthenosphere, and the water above it is relatively shallow. As seafloor spreading moves the lithosphere away from the ridge axis, the rocks cool and get thicker and denser. The farther it is from the ridge axis, the lower the lithosphere sits on the asthenosphere, and the deeper the water will be. This concept is known as the age-versus-depth relationship. Keeping in mind this relationship, why is the belt of shallow sea wider over the East Pacific Rise than over the Mid-Atlantic Ridge?
The belt of shallow sea is wider over the East Pacific Rise than over the Mid-Atlantic Ridge because it is younger and it's floating higher on the underlying asthenosphere which makes the water above more shallow.
Describe the age of the clasts in a sedimentary rock compared to the age of the sedimentary rock in which they are included. Explain.
The clasts in a sedimentary rock are older than the rock in which they are included.
What weathering history can you interpret from all fine-grained clay minerals with some hematite and limonite?
The clasts in this sedimentary rock are entirely products of chemical weathering, indicating extensive weathering. Preponderance of clay minerals indicates that the source rocks were made mostly of feldspars. Subordinate hematite and limonite indicate the presence of some ferromagnesian minerals.
Which will cool faster? Why?
The crust cools faster because more of the dough is in contact with cooler air, compared to the ball. In the ball, more dough is insulated from the surrounding air.
How does the mineral assemblage in chemically weathered sediment change with the amount of chemical weathering?
The more chemical weathering a sediment is subjected to, the fewer minerals there will be that are not resistant to weathering.
Explain how the process of seafloor spreading can produce these orientations and relationships.
The process of the seafloor spreading can produce these orientations and relationships because when the seafloor spreads, the plates move away each other at the center line of the mid ocean ridge. When the new lithosphere moves away from the center line to the edge of the ridge it causes the older crust to move away from the ridge.
Entrance to Zion National Park in Utah. A large cliff face contains thick beds of medium-grained white, gray, and beige sandstones displaying excellent cross bedding. Identify the rock and any sedimentary structures present, and interpret the depositional setting in which the rock formed.
The rock in this figure is sandstone. The sedimentary structures present are well sorted sandstone with large cross beds. There is also graded beds. The depositional setting in which the rock formed is deposited in a desert dune or in a current.
Where are the volcanic and earthquake patterns most similar?
They are most similar surrounding the Pacific Ocean and just north of the Red Sea.
Focus on the patterns in the middle of the Atlantic Ocean. Only a few volcanoes are shown along the Mid-Atlantic Ridge, but earthquakes seem to occur all along it. Volcanic activity does, in fact, occur all along the ridge. Why are only a few volcanoes shown?
This is a mature divergent boundary, which does not generally produce volcanoes that extend above water. The volcanism produced here is limited to the ocean floor alone.
Why do Alaskans have to worry about more volcanic hazards than Hawaiians? (You may wish to refer to your lecture notes about volcanoes to answer this question)
Volcanoes formed by tectonic collisions, like those in Alaska, tend to be stratovolcanoes. Stratovolcanoes produce violent eruptions with high amounts of thick, felsic pyroclastic material. Pyroclastic flows and ash falls are unique to these types of eruptions. The volcanoes of Hawaii form from a hot spot very close to the surface, and the lava often erupts while still mafic (basaltic), making it more fluid than stratovolcanoes. These types of volcanoes are shield volcanoes and although they are not as violent, they still pose the risk of destruction from lava, wildfires, and inhalation of volcanic gasses.
Now look at the contour lines as they cross these two streams. Their distinctive V shape tells us which way the streams are flowing. Suggest a "rule of V" that describes how those Vs reveal the direction of streamflow.
When crossing a stream or river, contour lines make "V"s that point upstream (uphill). Streams flow downhill, and so the stream flows in the opposite direction that the contour line is pointing.
What does the spacing between contour lines on a map reveal about the ground surface?
Wider spacing indicates gentle slopes and narrow spacing indicates steep slopes.
Which is older, the granite in Figure 12.3a or the xenoliths?
Xenoliths
The cement is very strong, and when scratched with a steel needle it has the same hardness as the grains. The cement consists of ________.
quartz
Along the coast, waves carry sand out into deeper, quieter water, where it accumulates and gradually becomes buried. A rock formed from sand grains cemented together is a(n) ________.
sedimentary rock
What grain shape is typical of wind-deposited sediment?
well rounded
What mineral changes would occur, and at what temperature and pressure, if Rock B was heated to 700°C and pressure on it was increased to 10 kbar? Select all that apply.
- Andalusite would change to Sillimanite at about 650 degrees C and 2.5 kbar. - Sillimanite would change to Kyanite at 700 degrees C and 6.5 kbar.
What parts of North America need not be concerned about local volcanic eruptions? Select all that apply.
- Eastern North/Central America - Central North America - Northeastern North America
Considering the principle of cross-cutting relationships, examine the granite and the two dikes in the Figure A (top photo). Indicate the sequence in which they intruded (e.g., 1, 2, 3).
- Granite (1) - Dike running side-to-side in photograph (2) - Dike running up-and-down through the photograph (3)
What volcanic hazards do Alaskans have to worry about that Hawaiians don't? Select all that apply.
- Pyroclastic flows - Local ash fall - Explosive blast - Lahars
Describe the sequence of aluminosilicate phase changes in Rock X and the T-P conditions and depths at which they occurred.
- Sillimanite experienced a reduction in pressure, but not much change in temperature. It eventually turned to Andalusite at just over 700 degrees C and about 1 kbar of pressure. - Andalusite turned to Kyanite at 450 degrees C and 2.5 kbar of pressure. - Kyanite experienced increasing pressures and temperatures, eventually turning to Sillimanite at 750 degrees C and 6.5 kbar of pressure.
In what parts of the world are there abundant earthquakes but not (apparently) active volcanoes?
- The length of the mid-Atlantic Ridge. - The western edge of the Nazca Plate. - The central and eastern United States - The Carribbean
What parts of North America have the greatest risk of problems associated with local volcanic eruptions? Why are volcanoes located there rather than in other regions?
- Western North/Central America - Alaska - Southern North/Central America
Why are volcanoes located there rather than in other regions? Select all that apply. You might refer to Figure 2.1 in Chapter 2 of your lab manual to answer this question.
- Western North/Central America has volcanoes because there are two collisions happening. The Juan de Fuca Plate makes an oceanic-continental collision with western North America, creating a continental island arc. Farther south, the Cocos Plate makes another oceanic-continental collision with North America in the region of southern California and Mexico. - Southern North/Central America has volcanoes because there are two collisions happening. The Cocos Plate makes an oceanic-continental collision with southern California and the western side of Mexico. Costa Rica and Panama (southern tip of Central America) are also impacted by the Nazca Plate, which produces another oceanic-continental collision. Both of these make an extensive continental volcanic arc. - Northern North America (near Alaska) has volcanoes because the Pacific Plate is moving to the northwest and crashing into the northernmost part of the North American Plate. This is an oceanic-oceanic convergence in the Northern Atlantic Ocean which creates a volcanic island chain we call the Aleutian Islands. Farther to the east, the Pacific Plate is colliding with the North American continent and producing a continental island arc in Alaska.
What is the relief between Little Tomah Lake and the top of Tomah Mountain? Write your answer in feet.
About 590', give or take a few feet.
How old is a rock if it contains a rubidium-87:strontium-87 ratio of 89.9?
About 780 million years old (.78 billion)
Which portrayal best shows direction?
All are equally effective.
What weathering history can you interpret from all quartz grains?
All of the nonresistant minerals have been removed by chemical weathering, leaving a mature sediment. Weathering likely occurred over a long period of time in order to remove the nonresistant minerals.
Describe what an area with closely spaced contour lines would look like compared to an area with widely spaced contour lines.
An area with closely spaced contour lines will have a steeply sloping surface and an area with widely spaced contour lines will be flat or gently sloping.
In Figure 9.7, how high is the highest point on the rim of the crater? Explain how you made this decision.
Between 300' and 350'. It goes beyond the highest contour line of 300', but not high enough to require another contour line. So, it but be higher than 300', but lower than 350'.
In Figure 9.4, what is the elevation of the highest point on Hunt Ridge? Write your answer in feet.
Between 720' and 740'.
In Figure 9.4, what is the elevation of the highest point on Farrow Mountain? Write your answer in feet.
Between 980' and 1000'.
Based on the average dormant interval following significant eruptions, predict when the next significant eruption is likely to occur.
Between the years 2050-2150
Does this plate consist of continental lithosphere, oceanic lithosphere, or both?
Both oceanic and continental lithosphere
Granite has been used throughout the ages for buildings (Fig. 4.7c, ii). What properties do you think make granite useful for construction?
I believe that granite is mainly used for buildings because it is more environmentally efficient because it can be recycled easily. I also believe that granite is good for preserving hot or cool air.
Explain why the ambiguous features you chose might be ambiguous.
I believe that the beard and hair color features might be ambiguous because as one ages their beard and hair color could change. After 30 years he could be bald or have grey hair. Also, beards can grow fast but they can also be removed quickly as well.
Explain why the diagnostic features you chose would still be diagnostic.
I believe that the features height and eye color would still be diagnostic today because those two features mainly stay constant in adults. 30 years ago he probably would have weighed less. As for the beard, he may have shaved it.
Some sculptures, however, are made of igneous rock, like the granite in Figure 4.7c, i and iii. Granite is made mostly of quartz, potassium feldspar, and plagioclase feldspar. How do the minerals in granite affect the ease with which sculptors can shape the stone?
I believe that the minerals in granite affect the ease with which sculptors can shape the stone because granite is and very hard rock which could make it difficult for sculptures to carve in it. With limestone or marble you could easily carve into it whereas granite you would have to chip into it.
What Do You Think? Every time Old Faithful spews steam into the air in Yellowstone National Park, it reminds us that there is hot magma beneath the park capable of producing an eruption. This deceptively peaceful volcanic activity is not the first to occur in the Yellowstone area. About 640,000 years ago, one of the most violent eruptions ever detected (VEI = 8, the maximum) blasted ash over much of the central and southwestern United States, blanketing the area shown in Figure 5.14 and dwarfing the areas affected by ash from other major eruptions. Comparison of the Yellowstone eruption with the effects of Mt. St. Helens gives us an idea of the difference between VEI 5 and VEI 8 eruptions. We cannot predict when or if a VEI 8 eruption will happen at Yellowstone again, but if it did, what would be its effect on the areas directly impacted by the ash? Which cities and states would suffer the most? Consider effects on the local economy, health, food supplies, and transportation networks. And although not all of the United States would be directly affected by the ash fall or explosion, what do you think the effects would be on the rest of the country?
I believe that the volcanic eruption would affect the surrounding states of Wyoming, Idaho, and Montana because they are the closest to Yellowstone. If a volcano was to erupt, Yellowstone would be affected by pyroclastic flows. The falling ash from the volcano would affect the rest of the country differently depending on how far away the states are. The further away that the states are, the amount of falling ash in the states would decrease. The Yellowstone volcanic eruption would cause major effects on the local economy because there would be a lot of ash in the area which is toxic for the people to breathe in. People would have to wear masks. The food and supplies such as water may be affected from the chemicals in the eruption. The eruption would compromise transportation networks and other communications because of the high quality of ash that may cause buildings to fall.
Some magnetic anomaly stripes are wider than others. Knowing what you do about seafloor spreading and magnetic reversals, suggest an explanation.
I would assume that some magnetic anomaly stripes are wider than others because when the new lithosphere moves in, there could have been different timings or rates on how fast or slow the seafloor was spreading at the time of the reversals.
What Do You Think? Loggers in eastern Maine excavated a hillside to look for material that they could use to build an access road for harvesting lumber and wood. The material they found is shown below in Figure E; note the small sledgehammer for scale.As foreperson for the lumbering team, would you recommend using this material to build the road, or would you direct the team to look for more suitable material? Consider the size, sorting, and shapes of the clasts, and whether the agent of their deposition will affect the suitability of the material for road building.
I would direct the team to look for more suitable material. The sorting is poor and the shapes of the clasts are irregular. I believe that the agent of their deposition will affect the suitability of the material for road building.
What weathering history can you interpret from nearly equal amounts of quartz, K-feldspar, and Na-plagioclase with a small amount of hematite?
It is possibly a granite (or quartzofeldspathic metamorphic rock) that had been weathered relatively quickly (because the feldspars were not altered to clay minerals) such that only the few ferromagnesian minerals in the parent rock were weathered to hematite.
What is the name of the plate on which the contiguous United States resides?
North American Plate
Has the Meiji seamount moved at a constant rate? Explain your reasoning.
The Meiji seamount has not moved at a constant rate because the rates of the other seamounts are much lower while the Meiji seamount is 71.4 Ma.
Why can't the principle of superposition be used to determine the relative ages of these rock layers?
The Principle of Superposition applies to undisturbed sequences of rocks, and all of these have been disturbed.
Explain your reasoning for both of the previous questions.
The ash fall rock would consist of glass shards melted together because the pyroclastic material falls quietly on the ground and gets compacted turning into a rock. A rock formed in a pyroclastic flow would happen fast causing ash and other large fragments to melt together quickly creating a rock that is made out of coarse volcanic bombs and rock fragments in a very fine-grained brown ash.
Which is the steepest side of Deadman's Mountain?
The eastern side
What can you say about the relative ages of the sedimentary rock layers in the Figure C (bottom photo)? What is the relative age of the folding compared to the age of the rocks?
The event which caused the folding must be younger (more recent) than the rocks.
Describe the relative age of the fault compared to the rocks it offsets in the Figure B (center photo).
The fault is younger than the rockit offsets.
Describe the slopes on both sides of Farrow Lake, the first lake west of Topsfield. Do the slopes on the east and west sides of the lake have the same steepness, or is one steeper than the other? Explain your reasoning.
The spacing of the contour lines on the east side of the lake is similar to the spacing on the west side. This tells me that the slopes have the same steepness on either side of the lake.
What transporting agents could be responsible for the moderately sorted clasts?
The transporting agents that could be responsible for the moderately sorted clasts would be a stream.
What transporting agents could be responsible for the poorly sorted clasts?
The transporting agents that could be responsible for the poorly sorted clasts would be glacial.
What transporting agents could be responsible for the very well-sorted clasts?
The transporting agents that could be responsible for the very well sorted clasts would be a wind-deposited sediment.
What weathering history can you interpret from rock fragments composed of Ca-plagioclase and pyroxene?
These fragments indicate that physical weathering was the dominant cause of breaking up the source rock. Since both of these minerals would alter rapidly during chemical weathering, weathering was either very rapid or there was little water available for chemical reactions. The source material was a mafic rock like gabbro.
Sandstone with preserved dinosaur trackway and asymmetric ripple marks. Note the different orientation of ripple marks in the foreground. Identify the rock and any sedimentary structures present, and interpret the depositional setting in which the rock formed.
This formation shows mud cracks in the sediment. The type of rock in this image is Limestone. A sedimentary structures that is present is cross bedding and mud cracks. There is also graded bedding and fossils. The depositional setting in which the rock formed is from terrestrial mud (riverbank deposits).
What weathering history can you interpret from a mixture of quartz grains and clay minerals?
This rock indicates an extensively weathered source material composed of quartz and clay minerals.
Which portrayal best shows changes in slope?
Topographic map and DEM are equally effective (and best).
Which portrayal best shows distance?
Topographic map and DEM are equally effective (and best).
Suggest two other properties that would be diagnostic despite the years that have passed.
Two other properties that would be diagnostic despite the years that have passed would be facial bone structure and head shape. Bone structure remains mostly the same as the years go on and same with the shape of ones head.
What grain shape is typical of glacial sediment?
angular
he cement (but not the grains) in the sandstone reacts when in contact with dilute HCl. The cement consists of ________.
calcite
Based on your answers above, which of the following correctly lists the three minerals mapped in this figure in order of increasing metamorphic grade.
chlorite, biotite, andalusite
What grain size can streams transport?
clay, silt, sand, and cobbles
Which rock(s) most likely formed in a pyroclastic flow?
coarse volcanic bombs and volcanic rock fragments in a very fine-grained brown ash
A rock containing large, rounded pebbles and cobbles indicates what about its depositional environment?
deposited by a swiftly moving stream
A cross-bedded sandstone indicates what about its depositional environment?
deposited in a desert dune or in a current
A black shale containing some pyrite crystals indicates what about its depositional environment?
deposited in an anoxic (oxygen-free) marine setting
A rock containing fossils of feathers indicates what about its depositional environment?
deposited in very quiet (stagnant) water
A sandstone containing symmetric ripples indicates what about its depositional environment?
deposited on a beach
Which of the following correctly ranks environments in the order in which you would expect sediments to become mineralogically mature, from slowest to fastest? Hint: Think about the temperature and the amount of rainfall available.
desert, temperate climate, tropical rain forest
What grain size can glaciers transport?
everything from clay to boulders
A rock containing more than 50% carbon and fossil leaves indicates what about its depositional environment?
formed from sediments accumulated in a swamp
A red mudstone containing dinosaur footprints indicates what about its depositional environment?
formed from terrestrial mud (riverbank deposits)
A rock containing fossils of intact coral indicates what about its depositional environment?
formed from warm-water, shallow marine reef
Which rock most likely formed in an ash fall?
glass shards welded together
Now look at the data for the South Pacific Ocean and its spreading center, the East Pacific Rise. Considering the width of this ocean, will the spreading rate be the same, greater, or less than that of the South Atlantic?
greater
A rock containing very angular grains indicates what about its depositional environment?
has not undergone a lot of transport
The sandstone, overall, has a reddish color. The cement contains ________.
hematite
Thick flows of glowing red lava engulf farms and villages on the flanks of Mt. Etna, a volcano in Sicily. The cold, black rock formed when these flows are cool enough to walk on is _______.
igneous rock
A poorly sorted arkose indicates what about its depositional environment?
immature, deposited close to the source
Which of the following mineral assemblages—as seen in Part 1.b-5.b —are mineralogically mature? Which are mineralogically immature?(i) All quartz grains(ii) Nearly equal amounts of quartz, K-feldspar, and Na-plagioclase with a small amount of hematite(iii) All fine-grained clay minerals with some hematite and limonite(iv) A mixture of quartz grains and clay minerals(v) Rock fragments composed of Ca-plagioclase and pyroxene
mature: (i), (iii), (iv); immature: (ii), (v)
The broad tundra plains of northern Canada expose gray, massive rock that formed many kilometers below a mountain belt. This rock, exposed only after the overlying rock was stripped away, is ________.
metamorphic rock
What sorting is typical of stream sediment?
moderate to good sorting
What grain shape is typical of stream sediment?
moderately rounded to well rounded
What sorting is typical of glacial sediment?
poorly sorted
Which portrayal best shows elevation?
topographic map
Which portrayal best shows location?
topographic map
Which portrayal best shows names of features?
topographic map
What sorting is typical of wind-deposited sediment?
well sorted
How far has the Meiji seamount moved from the hot spot? Explain your reasoning.
5,000 km
At what rate has the Pacific Plate moved based on data from the Kimei-Meiji segment?
55 km/Myr
A river segment is shown on a topographic map as being 3.5 inches long. How long (in miles) is that segment if the map scale is 1:24,000? If the map scale is 1:62,500? If the map scale is 1:100,000?
1.33 miles if scale is 1:24,000; 3.45 miles if scale is 1:62,500; 5.52 miles if scale is 1:100,000
Provide the width of the South Atlantic Ocean, as given in the left side of the figure
2,800 km
How old is a rock if it contains 6.2% of its original carbon-14 atoms?
22,920 years old
In what direction is the Pacific Plate moving today?
290°
Estimate the average rate at which the South Atlantic Ocean has been opening over the 80 million years for which data are provided.
3.5 cm/yr
Calculate the average rate of seafloor spreading for the South Atlantic Ocean over its entire existence.
33.3 km/Myr = 33.3 mm/yr
Assuming someone born today lives to the age of 100, how much wider will the Atlantic Ocean become during his or her lifetime?
333 cm
A red "X" in Figure 9.5 marks a spot on the shore of Baskahegan Lake, but the printed DEM doesn't say anything about its elevation. Use the topographic map (Fig. 9.4) to estimate the elevation of this point as accurately as possible. Write your answer in feet.
340'
Based on the age data on the bathymetric map, in what azimuth direction did the Pacific Plate move originally?
340°
What does the presence of these coral fossils suggest about the location of North America 370 million years ago?
370 million years ago, North America was probably rotated clockwise and positioned farther south, so that the locations of these fossil corals were situated in tropical and subtropical zones.
Measure the distance between South America and Africa along the fracture zone (indicated by the arrow) on the map in 2.3. What is the approximate distance in kilometers?
4,000 km
How many years ago did the Pacific Plate change direction?
40 Ma
A stretch of shoreline is 20 miles long. How long would it appear on a map at a scale of 1:24,000? At a scale of 1:62,500? At a scale of 1:100,000?
480,000 inches if scale is 1:24,000; 1,250,000 inches of scale is 1:62,500; 2,000,000 inches if scale is 1:100,000