Chapter 2 Gateway 1 Flashcards

1
Q

State 4 characteristics of the Earth’s core.

A
  1. Mostly iron and nickel
  2. Separated into liquid outer core and solid inner core
  3. Radius is about 3,500 km
  4. Temperature is between 3,000 to 5000 degree celsius
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2
Q

State 3 characteristic of the Earth’s mantle

A
  1. Mostly solid rock that flows under high temperature and pressure.
  2. 2,900 km thick
  3. Temperature between 800 to 3000 degree celsius
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3
Q

State 3 characteristics of crust.

A
  1. Basalt and granite rocks
  2. A few kilometers to more than 70 km thick.
  3. When the rocks in the lithosphere melt, hot molten rock known as magma is formed.
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4
Q

State the difference between oceanic crust and cotinental crust in terms of location, thickness and type and age of rock.

A

Oceanic crust is beneath deep oceans but continental is beneath the Earth’s continental masses and under shallow seas close to continent. Oceanic crust have a thickness between 5 and 8 km but continental crust have a thickness between 35 and 70 km. Oceanic crust consists of mainly Basalt, a heavy and dense rock but continental crust consists of lighter rock, including granite. Oceanic crust are rocks of less than 200 million years old but continental crust are rocks with a wide range of rocks ages, from very recent to nearly 4 billion years old.

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5
Q

State what happens when two oceanic plates diverge.

A

When the two plates move apart, fractures are form. Magma rises from the mantle, cools and solidifies. The magma form new sea floor known as mid-oceanic ridge. New rocks are closer to the mid-oceanic ridge and older rocks are further away. At various points of the mid-oceanic ridge, magma builds up and solidifies, forming underseas volcanoes. When these volcanoes grow above sea level, the are known as volcanic island.
Example: Mid-Altanic ridge is in the middle of the Atlantic Ocean, which is form when North Amercian plate and Eurasian plate diverge.
Example: A chain of volcanic island in the North Atlantic Ocean is the Azores

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6
Q

State what happens when 2 continental plates diverge.

A

When the two plates diverge, fractures are form. The land in between the two plates sink, forming a linear depression known as rift valley. An example include East African Rift valley form by the divergence of the Nubian boundary of the African plate and Somalian boundary of the African plate.

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7
Q

State what happens when two oceanic plate converge.

A

When two oceanic plate converge, the denser plate subduct under the less dense plate at the subduction zone. At the subduction zone, an oceanic trench is formed. The crust and uppermost mantle of the denser subducting plate melt, forming magma. Magma rises through the crust to form volcanoes on the less dense plate. Eventually, a chain or arc of island is form. Friction is created between the moving the rock when a plate subducts under another so earthquake may occur at the boundary. One example of two oceanic diverging is the Pacific plate subducts under the Philippine plate, forming Mariana Trench and Mariana Island.

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8
Q

State what happens when two continental plate converge.

A

When the two plates collide, both plate are thick and buoyant so both plates resist subduction. This causes the layers of rock on the upper part of the crust to be compressed together. They are folded upwards or sideways, creating fold mountain. One example of two continental plate converging is the Indian plate and the Eurasian plate, forming the Himalayas. [No trench, no melting of crust, no volcanoes]

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9
Q

State what happens when an oceanic plate converge with a continental plate.

A

When an oceanic plate converges with a continental plate, the denser oceanic plate subducts under less dense continental plate. An oceanic trench is formed at the subduction zone. The continental plate buckles and folds, forming fold mountain at the subduction zone, the crust and the uppermost mantle of the denser oceanic plate melt, forming magma. The magma rises through the crust, giving rise to volcanoes and volcanic eruption. Earthquake may also occur on the continental plate. An example of oceanic-continetal convergence can be found near the Sumatra where the Australian Plate subduct under a section of the Eurasian plate, forming the Sunda Trench.

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10
Q

State what happens at transform plate boundaries.

A

Plates slide past each other along transform plate boundaries. This movement results in the formation of a transform fault. In the process, tremendous stress builds up and is eventually release, often the in the form of violent earthquake. One transform plate boundary is the San Andreas Fault between Pacific Plate and the North American plate. In 1906, an earthquake occured in San Francisco, Southern California, at the San Andreas Fault. This caused several kilometers of the North American Plate to move an average of 2.5 meters, and at one point almost 7 meters in less than a minute.

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11
Q

Why do tectonic plate move?

A
  1. Convection currents are movements of heat within the mantle. Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread out beneath the plates
  2. This causes plates to be dragged along and to move away from each other.
  3. Then, the hot mantle material cools slightly and sinks, pulling the plates along.
  4. The sinking mantle material heats up again as it nears the core and the whole process repeats.
  5. Slab-pull force occurs when the dense, sinking oceans plate at subduction zones pulls the rest of the plate behind it. This is currently thought to be the main driving mechanism for plate movement.
  6. The subducting or sinking plate drives the downward-moving portion of convection currents.
  7. The mantle material which is found away from where the plates subduct drives the rising portion of convection currents.
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