Earth’s Internal Structure, Rock cycle, & Geologic time

The Earth’s Internal Composition

Question 1: What is the depth of the Kola borehole as a percentage of the Earth’s radius? Calculate using the following equation:

A. (123km / 637km) * 100 = 19.3%

B. (123km / 6370km) * 100 = 1.93%

C. (12.3km / 637km) * 100 = 1.93%

D. (12.3km / 6370km) * 100 = 0.193%

Question 2: What are alternative terms used in place of “extrusive” and “intrusive” igneous rock?

A. Magma and granite

B. Pumice and lava

C. Volcanic and plutonic

D. Vesicular and plutonic

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Question 3: During the Devonian Period, where is North America located relative to the Equator? (Hint: Go to “Close-up: Phanerozoic Eon,” then click on Devonian in the time scale image)

A. Predominately east of the equator

B. Predominately west of the equator

C. Predominately north of the equator

D. Predominately south of the equator

Question 4: The Hawaiian Islands are composed of linear chains of which of these types of volcano?

A. Cinder cones

B. Shield volcanoes

C. Stratovolcanoes

D. Lava domes

For the rest of this module, you will identify and explain the geographic distribution, patterns, and processes associated with Earth’s internal structure. In doing so, you will recognize and appreciate the impact the interior of the Earth has on the surface.

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GLOBAL PERSPECTIVE

Volcanoes are not randomly distributed across the globe; rather, their locations are distinct (commonly located on plate boundaries) and these patterns are evident at regional to global scales. Despite the potential dangers associated with volcanoes, many cities are located near areas susceptible to volcanic activity. In this section you will describe the spatial patterns of volcanoes and volcanic activity, and identify volcanoes located near populous cites.

Expand the GLOBAL PERSPECTIVE folder. Double-click and select the Mediterranean and W Asia folder.

Question 5: Where will you find the majority of volcanoes in Europe?

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A. France

B. Greece

C. Italy

D. Germany

Uncheck the Mediterranean and W Asia folder. Double-click and select Catania. Next, click on the Etna symbol in the Google Earth Viewer. Read about Mount Etna, located adjacent to the city of Catania on the Island of Sicily. To close the Smithsonian write-up on this volcano, click the X in the top right corner of the window.

Question 6: What type of volcano is Mount Etna?

A. Composite

B. Cinder cone

C. Shield

D. Crater

Uncheck the Catania folder. Double-click and select the Africa and Red Sea folder.

Question 7: Describe the general spatial pattern of volcanoes found on the continent of Africa (Hint: You might have to zoom in and out to view the spatial patterns of the volcanoes).

A. The volcanoes appear randomly distributed over most of Africa

B. Many are found along the Great African Rift valley located in eastern Africa

C. Many volcanoes form national borders of western and southern African countries

D. The majority are found within the Sahara Desert region located in northern Africa

Uncheck the Africa and Red Sea folder. Double-click and select Nairobi. Next, click on the Suswa symbol in the Google Earth Viewer. Read about Suswa, located west of the city of Nairobi, Kenya.

Question 8: What type of volcano is Suswa?

A. Composite

B. Cinder cone

C. Shield

D. Crater

Uncheck the Nairobi folder. Double-click and select Philippines and SE Asia.

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Question 9: Describe the general spatial pattern of volcanoes found in this region (Hint: You might have to zoom in and out to view the spatial patterns of the volcanoes).

A. The volcanoes appear randomly distributed over most of SE Asia

B. Many are found along the margins of this region

C. Many volcanoes form national borders among the island countries

D. The majority are found on the island of Borneo and are evenly spaced apart

Uncheck the Philippines and SE Asia folder. Double-click and select Jakarta. Next, click on the Pulosari, Perbakti-Gagak and Salak symbols in the Google Earth Viewer. Read about these volcanoes, located south of the city of Jakarta, Indonesia.

Question 10: What type of volcanoes are these?

A. Composite

B. Cinder cone

C. Shield

D. Crater

Uncheck the Jakarta folder. Double-click and select Hawaii and Pacific Ocean.

Question 11: Describe the general spatial pattern of volcanoes found in this region (Hint: You might have to zoom in and out to best view the spatial patterns of the volcanoes).

A. The volcanoes appear randomly distributed over most of the Pacific Ocean

B. Many are found along the margins of this region and near islands or island chains like Hawaii

C. Many volcanoes form national borders among the island countries

D. There are few volcanoes in the Pacific; as a result, there are no apparent trends regarding their spatial patterns

Uncheck the Hawaii and Pacific Ocean folder. Double-click and select Hawaii. Next, click on the Mauna Loa symbol in the Google Earth Viewer. Read about this volcano, located southwest of the city of Hilo, Hawai’I, USA.

Question 12: What type of volcano is Mauna Loa?

A. Composite

B. Cinder Cone

C. Shield

D. Crater

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Collapse and uncheck the GLOBAL PERSPECTIVES folder.

ROCK TYPES

As noted in the Introduction, all rocks can be classified as one of three basic rock types: igneous, sedimentary, or metamorphic.

Igneous rocks

Igneous rocks are further divided into extrusive igneous rock and intrusive igneous rock.

 Extrusive igneous rock is formed (cooled) on the Earth’s surface.

 Intrusive igneous rock is formed (cooled) in the Earth. Unless there has been significant erosion of surface material, intrusive igneous rock are not easily detectable on the surface (Figure 1).

Some intrusive igneous formations include:

o Dikes – vertical intrusive rock that formed from cooled magma within fissures that cut across older rock. Dikes frequently differ in composition to the surrounding bedrock.

o Sills – intrusive rocks formed in horizontal fissures. Sills are often situated between older layers of sedimentary rock.

o Batholith – a large pluton, or mass of rock that cooled and solidified deep within the Earth. Some batholiths are several hundred miles long.

Intrusive formations

(in red)

Figure 1. Igneous intrusive formation (Arbogast 2nd Ed).

Expand the ROCK TYPES and Igneous Rocks folders.

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Igneous rocks – Shiprock, NM

Double-click and expand the Shiprock, NM folder.

This feature is the remnant of a throat of a volcano, with radiating dikes. This volcano erupted over 27 million years ago.

Double-click the Ship Rock Tour link to view an animation.

Click Photo 1 for a different view.

Uncheck the Shiprock, NM folder.

Igneous rocks – Stone Mountain, GA

Double-click the Stone Mountain, GA folder.

This is a large pluton near Atlanta, GA that was formed during the Devonian period in the Paleozoic Era.

Double click the Stone Mountain Tour link to view an animation.

Click Photo 2 for a different view.

Uncheck the Stone Mountain, GA folder.

Igneous rocks – Krafla, Iceland

Double-click the Krafla, Iceland folder.

The dark areas are a lava flow from the Krafla volcano in Northern Iceland. The lava cooled formed basalt and rhyolite, which are extrusive igneous rocks.

Double click the Krafla Tour link to view an animation.

Click Photo 3 for a different view.

Uncheck the Krafla, Iceland folder.

Question 13: What is the difference between the two types of igneous rocks?

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A. The ages of the rocks. Intrusive rocks are always older

B. Extrusive rocks were formed in water, intrusive rocks were not

C. Intrusive rocks were formed in water, extrusive rocks were not

D. Intrusive rocks were formed in the Earth, extrusive rocks were not

Sedimentary rocks

Sedimentary rocks are formed by the deposition of sediments (usually in a marine environment) that under pressure slowly turn into rock. Lithification (cementing of sediment into rock) is an important process in the formation of this type of rock.

There are three board types of sedimentary rock: organic, clastic, and chemical precipitation.

 Organic sedimentary rocks are formed from the deposition of carbon based material. Subjected to pressure, this material, over time, can form coal.

 Clastic sedimentary rocks are sedimentary rocks composed of clasts or pieces of weathered and eroded rocks. They are classified by grain size and range from fine grained claystone (Figure 2) to coarse grained conglomerate (Figure 3).

Figure 2. Claystone (Wikipedia).

Figure 3. Conglomerate (Wikimedia).

 Chemically precipitated sedimentary rocks are formed through the precipitation of calcium carbonate which is then deposited on the ocean floor. Over time, enough pressure can built such that lithification occurs creating this type of sedimentary rock. Limestone is a common example of a chemical precipitated sedimentary rock.

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Expand the Sedimentary Rocks folder.

Sedimentary rocks – West Virginia

Double-click the West Virginia folder.

This is a coal mine in West Virginia, where mountain top removal is a common way of mining this sedimentary rock. Coal is an economically important sedimentary rock worldwide as nearly 40 percent of the electricity generated comes from coal power plants (Worldcoal, 2006).

Click Photo 4 for a different view.

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Sedimentary rocks – Grand Canyon

Double-click the Grand Canyon, AZ folder.

The Grand Canyon is a showcase of clastic sedimentary rock. Erosion by the Colorado River, coupled with tectonic uplift, has exposed layers of different types of largely sedimentary rock dating back nearly 2 billion years to the Proterozoic period in the late Precambrian Era.

Click the Grand Canyon Rock Layers folder to see an illustration of a cross section of the Grand Canyon.

Question 14: Why are there no rock layers younger than the Kaibab formation?

A. All the rock layers are younger than the Kaibab formation

B. The Kaibab formation was the last layer to be deposited

C. The Colorado River eroded younger layers

D. The Great Unconformity is younger

Click Photo 5 to see various rock layers in the Grand Canyon.

Uncheck the Grand Canyon, AZ folder.

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Sedimentary rocks – Rocky Mountains

Double-click the Rocky Mountains folder.

The Rocky Mountains in Canada are comprised primarily of limestone and shale, suggesting at one time this area was once covered by an ocean. Scientists estimate this limestone was created during the Paleozoic Era (350 million years ago), and that uplift to create the mountains began during the last half of the Mesozoic Era (180 million years ago) (Gadd, 2008).

Click Photo 6 to see various rock layers in the Rocky Mountains.

Question 15: Which type of sedimentary rock (organic, clastic or chemical precipitated) is present in this photo?

A. Organic

B. Clastic

C. Igneous

D. Chemically precipitated

Question 16: Describe why the process of lithification is important in the formation of sedimentary rocks.

A. It binds sediments into a solid mass through compaction

B. It adds a lithium which chemically binds the sediments into a rock

C. Lithification does not play a part in the formation of sedimentary rocks

D. Lithification only plays a roles with clastic sedimentary rock formation

Uncheck the Rocky Mountains folder.

Metamorphic rocks

Figure 4. Gneiss, foliated (Wikimedia).

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Metamorphic rocks are formed from igneous or sedimentary rocks that have been subjected to heat and pressure; in other words, the heat and pressure results in the rearrangement or recrystallization of minerals to form different minerals.

Metamorphic rocks formed from igneous rocks are sometimes called meta-igneous. Likewise, meta-sedimentary rocks are metamorphic rocks formed from sedimentary rocks.

Common metamorphic rocks include marble (from limestone) and gneiss (usually from granite).

Metamorphic rocks are divided into two broad categories, foliated and non-foliated:

 Foliated metamorphic rocks (Figure 3) exhibit banding as the minerals present align to form bands.

 Non-foliated rocks (Figure 4) lack this banding.

Metamorphoses can occur in two ways, namely contact metamorphism and regional metamorphism. The former happens over a small area and entails magma coming in direct contact with rock. The heat from the magma alters the crystal structure of the rock. The latter occurs over a much larger area and entails high heat and great pressure altering rock.

Expand the Metamorphic Rocks folder.

Metamorphic rocks – Jeff Davis Peak

Double-click and select the Jeff Davis Peak folder.

This is Jeff Davis peak which is comprised primarily of quartzite, a metamorphic rock formed from sandstone.

Double-click the Jeff Davis Peak Tour link to view an animation.

Click Photo 7 to see various rock layers of quartzite.

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Figure 5. Marble, non-foliated (Wikimedia).

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Metamorphic rocks – Carrara, Italy

Double-click and select the Carrara Italy folder.

The white areas are marble quarries near Carrara, Italy, not far from Pisa. The area is well known for Carrara marble which is found in the surrounding mountains. This marble is used for statues and buildings such as the Pantheon in Rome.

Click Photo 8 to see a Carrara marble quarry.

Question 17: Why is contact metamorphism restricted to a small area?

A. Because the body of protruding lava which causes contact metamorphism is relatively small in size

B. Because the body of protruding magma causes contact metamorphism is relatively small in size

C. Because only certain rocks can be metamorphosed and they are generally found in small quantities

D. Because all metamorphoses are restricted to small areas

Collapse and Uncheck the ROCK TYPES folder.

EARTH’S INTERIOR

By interpreting seismic waves from earthquakes, scientists have divided the Earth’s interior into three major sections: core, mantle, and crust.

Click Earth’s Interior and use the illustration to identify the layers in the table below. Select the correct answer from the list provided below.

Layer

Composition

Structure

Depth

Q18

Iron

Liquid

2250 km

Q19

Iron & Nickel

Solid

1220 km

Q20

Iron, Magnesium & Silicon

Solid

2230 km

Q21

Nickel

Viscous

250-425 km

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A. Lower Mantle

B. Outer core

C. Inner core

D. Asthenosphere

E. Upper mantle

F. Lithosphere

Question 22: Explain how the structure of rock changes as you go from the lithosphere through the asthenosphere and upper mantle.

A. Solid rock, semi-solid rock, molten rock

B. Solid rock, molten rock, semi-solid rock

C. Semi-solid rock, molten rock, solid rock

D. Molten rock, solid rock, semi-solid rock

Collapse and Uncheck EARTH’S INTERIOR.

VOLCANOES

Volcanoes are divided into three types: cinder cone, composite, (or stratovolcano) and shield. These classifications are based largely on whether the eruption is fluid or explosive in nature.

Expand the VOLCANOES folder. Double-click the Capulin Mountain Tour link to view an animation.

This is Capulin Mountain in New Mexico. It is a cinder cone volcano. Cinder cone volcanoes are the smallest of the three types of volcanoes and are characterized by steep sides.

Double click and check the Folsom, NM box.

Double-click and select Folsom, NM.

Question 23: What is the contour interval of this map?

A. 1:24,000

B. 20 meters

C. 20 feet

D. 1929

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Question 24: Based on the contour lines, what is the highest elevation on this volcano?

A. 8,000 feet

B. 8,128 feet

C. 8,182 feet

D. 8,218 feet

Question 25: Based on the contour lines, what is the elevation in the center of the crater?

A. 7,800 feet

B. 7,775 feet

C. 8,125 feet

D. 7,900 feet

Uncheck Folsom, NM and then check Profile #1.

Right-click Profile #1 and then select Show Elevation Profile.

Question 26: What is the diameter of the volcano in miles?

A. 0.75 miles

B. 0.39 miles

C. 0.93 miles

D. 2.1 miles

Question 27: What is the average slope of the profile line?

A. 60.8%

B. 794 feet

C. 39.8%

D. 91.2%

Close the Elevation profile window and uncheck Profile #1.

Double click the Mount Baker Tour link to view an animation.

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Double-click and select Mt. Baker, WA.

This is Mt. Baker in Washington State. It is a composite volcano, which grows over the course of several eruptions. They can remain inactive for hundreds of years, but when they do erupt, they tend to be quite explosive.

Question 28: What is the contour interval, in feet, of this map?

A. 1:24,000

B. 40 meters

C. 40 feet

D. 1989

Question 29: What is the highest elevation, in feet, on this volcano?

A. 10,000 feet

B. 10,700 feet

C. 10,780 feet

D. 10, 870 feet

Uncheck Mt. Baker, WA and then check Profile #2.

Right-click Profile #2 and then select Show Elevation Profile.

Question 30: What is the approximate diameter (in miles) of the volcano?

A. 1.5 miles

B. 7 miles

C. 5.7 miles

D. 2.6 miles

Question 31: What is the average slope of the profile line?

A. 89%

B. 32%

C. 92%

D. 78%

Close the Elevation profile window and uncheck Profile #2.

Double click the Kilauea Tour link to view an animation.

Double-click and select Kilauea Crater.

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This is the Kilauea volcano on the island of Hawai’i. It is a shield volcano, whose eruptions are characterized as being fluid and non-explosive – notice the parking lot near the crater.

Question 32: What is the highest elevation of a benchmark (look for “BM” on map) on this volcano in feet?

A. 3,635 feet

B. 3,885 feet

C. 4,078 feet

D. 3,524 feet

Question 33: What is the elevation of the benchmark (denoted by an “X”) in Halema’uma’u Crater?

A. 3,421 feet

B. 4,231 feet

C. 2,431 feet

D. 3,412 feet

Uncheck Kilauea Crater and then check Profile #3.

Right-click Profile #3 and then select Show Elevation Profile.

Question 34: What is the approximate diameter of the volcano in miles?

A. 24.5 miles

B. 16.9 miles

C. 32.8 miles

D. 18.5 miles

Question 35: What is the average slope of the profile line?

A. 63.1%

B. 3.3%

C. 10.8%

D. 2.9%

Collapse and uncheck the VOLCANOES folder.

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ROCK CYCLE

Thus far, we know how each type of rock is formed. This section addresses the rock cycle that examines the processes and conditions in which one rock type is changed into another.

Click ROCK CYCLE and answer the following questions:

Question 36: Which process changes igneous rock to sedimentary rock?

A. Cooling that results in crystallization Cooling

B. Heating and pressure which leads to melting

C. Heating and pressure which leads to recrystallization

D. Weathering, erosion and deposition

Question 37: Which process changes sedimentary rock to metamorphic rock?

A. Cooling that results in crystallization

B. Heating and pressure which leads to melting

C. Heating and pressure which leads to recrystallization

D. Weathering, erosion and deposition

Question 38: Which process changes igneous rock to metamorphic rock?

A. Cooling that results in crystallization

B. Heating and pressure which leads to melting

C. Heating and pressure which leads to recrystallization

D. Weathering, erosion and deposition

Question 39: Which process changes metamorphic rock to sedimentary rock?

A. Cooling that results in crystallization

B. Heating and pressure which leads to melting

C. Heating and pressure which leads to recrystallization

D. Weathering, erosion and deposition

Question 40: Which process changes magma to igneous rock?

A. Cooling that results in crystallization

B. Heating and pressure which leads to melting

C. Heating and pressure which leads to recrystallization

D. Weathering, erosion and deposition

Uncheck the ROCK CYCLE folder.

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REFERENCES