Marine Biology Chapter 16 - Geology of the Ocean
Molten material within the mantle is called __________.
Magma
The magma that flows through the mid-ocean ridge comes up from the...?
Mantle
The structure labeled "C" in the diagram is the...?
Mantle
Magma
Molten material within Earth's mantle (called lava at Earth's surface)
Subduction
Occurs when one crustal plate plunges down under another
The largest area of ocean floor is the...?
Ocean Basin
Which topographical features are in the proper sequence, going from the Mid-Atlantic Ridge to the North American continent?
Ocean basin, slope, shelf
Which of the following items is not a topographical feature?
Oil deposits
The original supercontinent that existed about 200 million years ago is called...?
Pangaea
The theory of __________ explains continental drift.
Plate Tectonics
How were the Hawaiian Islands formed? Are they all the same age?
The Hawaiian Islands were formed from a chain of seamounts. The main island of Hawaii, at the eastern end of the chain, is the youngest (formed about 800,000 years ago) and most geologically active of the five Hawaiian Islands. The progressively older seamounts stretch in an arc to the northwest. The oldest Hawaiian Island is about 4 to 6 million years old.
Mid-Ocean Ridge
Undersea volcanic mountain range that encircles the globe
If sound travels 1454 meters per second in water, how deep is the ocean floor if the echo of a ship's signal takes one second to return to the surface?
727 meters
How was the Mid-Atlantic Ridge formed? Explain how the process is related to seafloor spreading.
A convection current is a transfer of heat in a liquid or gas that causes the molten magma to rise up through the mantle and into the crust, forming an oceanic ridge. Off the east coast of North and South America, it is the Mid-Atlantic Ridge that is formed; this ridge runs the entire length of the Atlantic Ocean, dividing it in half. Magma that breaks through Earth's oceanic crust as lava can also accumulate to form mid-ocean islands. The upward movement of magma under the Mid-Atlantic Ridge causes seafloor spreading, which is the moving apart of the plates. The North American and South American plates move westward, while the Eurasian and African plates move eastward. As the hot magma rises under the Mid-Atlantic Ridge, cooler magma moves in to take its place. This sets up a continuous circulation pattern similar to the circulation of warm air in a room.
Fringing Reef
A coral reef that grows a few kilometers offshore, parallel to the mainland
Barrier Reef
A coral reef that grows about 25 kilometers offshore, separated by a channel from the mainland
Fault
A crack in Earth's crust that occurs at the margin of two plates
What are deltas and how are they formed?
A delta is a fan-shaped feature formed by sediments that pile up at a river's mouth
Rift Valley
A depression that runs along the crest of the mid-ocean ridge
Delta
A fan-shaped feature formed by sediments that pile up at a river's mouth
Explain how seamounts are related to guyots and islands.
A guyot is the flat top of a seamount, islands form when the seamounts with guyots get tall enough. Some seamounts actually may be former islands that have sunk beneath the surface. Erosion by waves and currents can cause the tops of seamounts to become flattened, forming structures called guyots
Convection Current
Continual movement of gas or liquid in a cycle as the heated part rises and the cooler part sinks; inside Earth, causes molten magma to rise from mantle into crust; in atmosphere, causes breezes
Darwin hypothesized that the last stage in coral reef evolution is the...?
Coral Atoll
Trenches
Deepest, steepest depressions on ocean floor, formed by subduction
The fan-shaped feature that is formed by a river depositing sediments near the shore is a...?
Delta
Calculate the depth of a sunken ship if a sonar signal takes two seconds to return to the research ship after it is emitted.
Depth (D) = 1454 meters per second ✕ time (t) ÷2 In this example, D = 1454 ✕ (2 ÷ 2) D = 1454 meters
Crust
Earth's surface layer (above mantle), about 40 kilometers thick
What are three common sources of beach sand?
Erosion from rocks, pebbles formed by waves, and rock eroded by mountains
A __________ is where black smokers emerge in a rift zone.
Hydrothermal Vent
Fjord
A steep, deep, narrow inlet from the sea formed by the action of glaciers
Atoll
A string of coral islands that form a circle (around a sunken island)
The scientist most responsible for formulating the theory of continental drift is...?
Alfred Wegener
Hydrothermal Vent
An area in the rift zone at which hot springs emerge
Hot Spot
An area of intense geological activity in the crust where a seamount forms
How do coral atolls form? How are they related to reefs?
An atoll is a string of coral islands that forms a circle. In the middle is a shallow lagoon that may vary in width from 1 to 12 km. In 1837, the naturalist Charles Darwin observed these islands as he sailed on the research vessel H.M.S. Beagle, and he wondered why the islands form a circle. He hypothesized that the circular shape represents the last stage in reef evolution, which is associated with the sinking of a volcanic island. According to Darwin, a fringing reef appears first along the shoreline of a volcanic island. While the island begins slowly to sink or erode, the fringing reef continues to grow upward and outward to form a barrier reef. Finally, the island sinks completely below the surface, leaving only a circular fringe of reefs, that is, the atoll. Scientists have confirmed Darwin's hypothesis by drilling through the coral limestone and discovering a foundation of volcanic rock beneath the reef.
Continental Slope
Area where seafloor drops steeply at outer edge of continental shelf
How did the stars and planets come into being?
At the time of the big bang, all the matter in the universe was contained in one sphere. Extremely hot and dense, the sphere exploded, sending out matter in all directions in a kind of giant cloud. As the cloud moved out from the explosion, some of the matter came together and formed clumps that eventually became galaxies—including the Milky Way, the home galaxy of planet Earth. In time, further clumping of the matter caused the formation of stars and planets.
What important geological process occurs in a rift zone?
Continental drift: the rift is a crack in the seafloor through which molten rock from the mantle is expelled. When the hot magma pours out on the ocean floor, it cools and solidifies to form new ocean crust. Lateral movements on both sides of the rift then cause the seafloor to spread apart. Over geologic time, hot molten matter rising up through the mantle and into the crust causes continents to split apart. The continuing flow of magma pushed the continents farther apart and created a space between them.
Guyots
Flattened undersea structures formed when tops of seamounts are eroded by waves and currents
Island Arcs
Groups of volcanic islands that form an arc near an ocean trench
A __________ is an area of intense activity in the mantle.
Hot Spot
What forces caused the supercontinent Pangaea to split apart?
Powerful forces inside Earth's interior caused the breakup of the continents. The interior of our planet is com- posed of several layers. At Earth's center is the inner core, surrounded by the outer core, the mantle, and then the crust. Much of Earth's interior is in a hot, molten state. The inner core has the highest temperatures, with a range of about 6200 to 6600°C. The mantle, which is a region of geologic activity between the core and the crust, has a temperature range of about 1200 to 5000°C. The high temperatures inside Earth are hot enough to melt rock. In fact, Earth's interior—from the inner core to the upper mantle—consists of hot, molten material. This molten material within the mantle is called magma. The churning of the magma creates a force that generates great pressures upward into Earth's surface layer, or crust. Earth's crust is only about 40 km thick. If enough force is generated, it cracks. Then the ground trembles and moves, producing an earthquake. Sometimes magma flows out of a crack in the Earth's crust, producing a volcanic eruption. Magma that flows out of the crust onto Earth's surface is called lava. Disturbances (vibrations) in Earth's crust, such as volcanic eruptions and earthquakes, are examples of seismic activity. Seismic activity was involved in the breakup of the supercontinent Pangaea.
What process causes the continents to drift apart? How?
Powerful forces inside Earth's interior caused the breakup of the continents. The interior of our planet is com- posed of several layers. At Earth's center is the inner core, surrounded by the outer core, the mantle, and then the crust. Much of Earth's interior is in a hot, molten state. The inner core has the highest temperatures, with a range of about 6200 to 6600°C. The mantle, which is a region of geologic activity between the core and the crust, has a temperature range of about 1200 to 5000°C. The high temperatures inside Earth are hot enough to melt rock. In fact, Earth's interior—from the inner core to the upper mantle—consists of hot, molten material. This molten material within the mantle is called magma. The churning of the magma creates a force that generates great pressures upward into Earth's surface layer, or crust. Earth's crust is only about 40 km thick. If enough force is generated, it cracks. Then the ground trembles and moves, producing an earthquake. Sometimes magma flows out of a crack in the Earth's crust, producing a volcanic eruption. Magma that flows out of the crust onto Earth's surface is called lava. Disturbances (vibrations) in Earth's crust, such as volcanic eruptions and earthquakes, are examples of seismic activity. Seismic activity was involved in the breakup of the supercontinent Pangaea.
Mantle
Region of geological activity between the Earth's core and crust
Plates
Segments of Earth's crust that float (with the continents on top) on the mantle
Continental Rise
Slightly elevated region formed at base of continental slope by accumulation of mudslide sediments
Keys (Cays)
Small islands that form when chunks of coral stone break off from reefs and accumulate on the seafloor
Seamounts
Small undersea mountains formed by lava piling up on seafloor; they form over hot spots in the mantle
What were the sources of the ocean's water?
Some of the ocean's water came from the activity of volcanoes, which spewed great quantities of water vapor into the atmosphere. The impact of many meteors, which heated the surface of Earth, is also thought to have caused the release of water vapor. In addition, heated water in the crust boiled up to the surface and formed hot springs. Some of the hot water emerged from the surface as a geyser, or spray. In some places on Earth today, hot springs and geysers still exist, which are evidence that the area beneath them is hot.
Submarine Canyons
Steep, v-shaped depressions that cut through the continental shelf; extensions of sunken river valleys
Topography
Study of Earth's surface features, on land and on the ocean floo
Deep-sea trenches are caused by...?
Subduction
The crust of one plate plunges below another during __________.
Subduction
Which is not an accurate statement about plate tectonics?
The continents are fixed in position
What natural process is illustrated in the following diagram?
The evolution of a coral (reef) atoll
A feature of the seafloor that provides evidence for the theory of plate tectonics is...?
The mid-ocean ridge
Seafloor Spreading
The moving apart of Earth's plates caused by the upward movement of magma under the mid-ocean ridge
Based on this profile of the ocean floor, which statement is correct?
The sides of the ridge are moving away from each other
Why is the theory of plate tectonics called a unifying theory?
The theory of plate tectonics is called a unifying theory because it explains the origin of, and connections between, such phenomena as earthquakes, volcanic activity, faults, continental drift, and seafloor spreading. Knowledge of plate tectonics is also helpful in explaining how some structures on the ocean floor were formed.
What is an accurate statement regarding the data in this diagram?
The topographic features on both sides of the ridge are very similar
Plate Tectonics
Theory that Earth's crustal plates float on the mantle
Continental Drift
Theory that the continents once formed one large landmass, then broke apart and drifted to their present positions
Describe some of the evidence that indicates the continents originated from a single landmass.
Wegener cited the similarities of fossils and rock formations on different continents (especially on either side of the Atlantic) along with other technical evidence to support his hypothesis, which he called the theory of continental drift. His theory was not well received by most geologists at that time. In fact, scientists were quick to point out that Wegener was not even a geologist; he was a meteorologist—a scientist who normally studies the weather. However, studies of the seafloor that were con- ducted in the 1950s provided more evidence to confirm Wegener's theory, and it is now generally accepted by the scientific community
Why are some rocky coasts (with fjords) so steep?
When the climate warms, the glaciers move, creating deep valleys and troughs