LET Review about geology and science as it relates to the earth and its composition are located here.
1. Around what body of water will you find the region known as the Ring of Fire?
A. Pacific Ocean
B. Arctic Ocean
C. Atlantic Ocean
D. Indian Ocean
Correct Answer: A
As shown in the diagram, the Pacific Ocean is surrounded by zones of high volcanic and seismic activity. Some of the world's best-known volcanoes are found there, and over three quarters of all major earthquakes occur in the Ring of Fire. The diagram used for this question does not show the bottom part of the ring - the volcanic activity extends south to Antarctica. The oceans have been renamed, and the part of the Pacific Ocean which used to border Antarctica has been renamed the Southern Ocean. The pink line in the diagram terminates at the latitude where the name changes, but the ocean is continuous, and the plates also extend to the south.
2. The current explanation for the geologic processes behind the Ring of Fire is that large pieces of the Earth's surface, called plates, are moving around. What is the name for the field of study which investigates this motion?
A. Terrology
B. Plate tectonics
C. Oceanography
D. Crust kinematics
Correct Answer: B.
This basic idea was introduced to the world in 1912 by Alfred Wegner, who proposed what he called Continental Drift. The model has developed over the last century, and is far more sophisticated in the detail it can provide about the physical and chemical processes involved, but the principle remains the same. The lithosphere (the crust and the upper part of the mantle) is made up of plates, which can float across the surface of the asthenosphere (the more fluid part of the mantle immediately below the lithosphere). The movement of the plates means they run into each other, or move past each other, or separate from each other, at various points. The places where plates interact tend to be the sites of earthquakes and volcanoes.
3. On the west coast of South America, the Andes Mountains are the visible product of an ongoing process in which an oceanic plate runs into a continental plate, and slides underneath it. What is the term used to describe this process?
A. subduction
B. conduction
C. induction
D. convection
Correct Answer: A.
Plates that are running into each other are called convergent plates, or destructive margins. The result of the collision when both plates are continental is uplift mountains, such as the formation of the Himalayas as the Indian Plate collides with the Asian Plate. When one of them is an oceanic plate, that plate slides down to the asthenosphere or to the lower mantle, and is destroyed. The area where this happens is the site of earthquakes, volcanoes and mountain building. Subduction is responsible for much of the activity along the eastern part of the Pacific Ocean.
4. What is the name of the plate that is involved in convergence with the South American Plate along most of the western coast of South America?
A. Pacific Plate
B. Nazca Plate
C. Caribbean Plate
D. Scotia Plate
Correct Answer: B.
The eastern part of the Ring of Fire is mostly caused by the subduction of the Nazca Plate and the Cocos Plate. The larger of these is the Nazca Plate, named after a region in Peru. It is primarily responsible for the formation of the Andes mountain range, and is the reason why Chile and Peru have as many volcanoes and earthquakes as they do, including the largest earthquake ever recorded, the Great Chilean Earthquake, with its epicentre at Lumaco. Occurring on 22 May 1960, it recorded 9.5 on the Richter scale used to measure earthquake magnitudes.
5. The Cocos Plate is largely responsible for Mexico's very active volcanoes. Which of these volcanoes is NOT found in the Trans-Mexican Volcanic Belt, which is also called the Sierra Nevada?
A. Parícutin
B. Pico de Orizaba
C. Kilimanjaro
D. Popocatépetl
Correct Answer: C.
Pico de Orizaba is the highest point in Mexico, and is a currently-dormant stratovolcano. Popocatépetl (pictured in the question) is the country's second-highest peak, and by far its most active volcano. Until the end of the 20th century it had glaciers on its summit, but they have disappeared, primarily due to the heat generated by volcanic activity. Parícutin is a cinder-cone volcano which is unique because its formation has been completely documented. It started from a fissure in a farmer's field in 1943, and the first ejection of ash and stone was witnessed by the family. Media coverage excitedly followed, so the cone growth until activity subsided in 1952 was thoroughly recorded.
Kilimanjaro, one of the world's most recognisable volcanoes, is in Africa,not Mexico.
6. Mt St Helens, shown here during its 1980 eruption, is probably the best-known of the volcanoes along the west coast of North America, but it is only one of 20 major volcanoes and over 4,000 volcanic vents in the area where the Gorda and Juan de Fuca plates are converging on the North American plate along the Cascadia Fault. What is the name given to this region?
A. Western American Volcanic Zone
B. Juan de Fuca Volcanic Zone
C. Cascadia Volcanic Zone
D. Gorda Volcanic Zone
Correct Answer: C.
The Cascadia Volcanic Zone runs from northern California to Vancouver Island in British Columbia. The mechanics of this subduction zone are unusual,as there is no oceanic trench associated with it. The colliding plates scrape directly past each other, and material from the oceanic plate is transferred to the continental plate, forcing mountains upwards, in a process called accretion.
7. Canada's Northern Cordillera Volcanic Province, which contains most of Canada's most active volcanoes, is unusual because its activity is caused by the Pacific Plate moving past the North American Plate along the Queen Charlotte Fault. The resulting extension of the continental plate leads to volcanic activity through a process more commonly found in the middle of oceans. What is it called?
A. ripping
B. spreading
C. rifting
D. stretching
Correct Answer: C.
The separation of plates from one another in the middle of oceans means that magma emerges, and underwater volcanic mountain ranges are formed. These ranges are the indicators of mid-ocean plate boundaries. In the Northern Cordillera Volcanic Province, the plate interaction means that portions of the North American Plate are being pulled apart, leaving a weakness in the crust that leads to vulcanism. The process is called rifting, and the resultant volcanoes are called rift volcanoes. Faulting and extensional cracking are also involved in the region's volcanic activity.
8. Russia's Kamachatka Peninsula, on the northwest 'corner' of the Ring of Fire, has a number of active volcanoes, of several different types, including both stratovolcanoes and shield volcanoes. Which type of volcano is shown in this photo taken from the International Space Station?
A. Shield volcano
B. Stratovolcano
C. Neither of these
D. Both of these
Correct Answer: D.
Stratovolcanoes, also called composite volcanoes, are formed when the eruptions produce thick lava which hardens before moving very far. They usually have steep sides, and are prone to explosive eruptions. The most prominent peak in the photo is Kronotsky, a stratovolcano which last erupted in 1923.
Shield volcanoes are formed by more fluid lava, which spreads out over a larger distance before cooling sufficiently to harden. They are relatively broad and flat,hence their name - they resemble the shape of a shield laid on the ground. The rounded shield volcano to the right of Kronotsky in the photo is Schmidt Volcano, which is not known to have erupted in human memory.
Kamchatka also has volcanic types that are not as common as the two described here, including lava domes and fissure vents.
9. Indonesia has some of the most active volcanoes in the world, due to its location at the site of convergence of three different plates. Which three plates are they?
A. Pacific, Eurasian and Australian
B. Eurasian, Filipino and North American
C. African, Indian and Arabian
D. Pacific, Antarctic and Nazca
Correct Answer: D.
Indonesia has been the site of some of the largest volcanic explosions ever recorded. Lake Toba, in northern Sumatra, is in the caldera of a volcano whose eruption around 75,000 years ago is believed from archaeological evidence to have produced a worldwide volcanic winter lasting up to five or six years. In 1815, the eruption of Mount Tambora, in Sumbawa, was responsible for what was called 'The Year Without a Summer' due to the ash it produced. The 1883 eruption of Krakatau, a volcanic island located west of Java (no matter what the movie title says) is considered to have produced the loudest sound ever generated on the surface of the earth.
10. The southern part of the Ring of Fire lies along the northern edge of Antarctica. Most of the volcanic activity is caused by extensional processes. What is the name of the mid-ocean ridge where much of the activity occurs?
A. Mid-Antarctic Ridge
B. Pacific-Antarctic Ridge
C. Southern Ridge
D. Antarctic Ridge
Correct Answer: D.
The ridge is named because the Pacific and Antarctic plates are separating along its length, producing an underwater volcanic mountain range. Mount Erebus, the world's most southerly active volcano, is located on Ross Island, off the coast of Victoria Land. This region, which is near the western end of the Antarctic portion of the Ring of Fire, contains many of the best known Antarctic volcanoes. The other end, along the Antarctic Peninsula, contains the only local subduction zone, and is often considered to be an extension of the Andes Volcanic Zone with which we started our tour.
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