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Questions and Answers
What is a characteristic feature of a transform boundary?
What is a characteristic feature of a transform boundary?
What technological advancement allowed geologists to measure tectonic plate movement accurately?
What technological advancement allowed geologists to measure tectonic plate movement accurately?
What drives the movement of tectonic plates according to the convection process?
What drives the movement of tectonic plates according to the convection process?
How do tectonic plates move during subduction?
How do tectonic plates move during subduction?
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What does the term density refer to in the context of tectonic plates?
What does the term density refer to in the context of tectonic plates?
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What does the theory of plate tectonics describe about Earth's surface?
What does the theory of plate tectonics describe about Earth's surface?
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Which part of the Earth is described as the outermost layer?
Which part of the Earth is described as the outermost layer?
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What type of boundary occurs when two tectonic plates move away from each other?
What type of boundary occurs when two tectonic plates move away from each other?
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What happens at a convergent boundary?
What happens at a convergent boundary?
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What distinguishes the asthenosphere from the lithosphere?
What distinguishes the asthenosphere from the lithosphere?
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What geological feature can result from the movement of tectonic plates?
What geological feature can result from the movement of tectonic plates?
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How many large tectonic plates are currently recognized on Earth?
How many large tectonic plates are currently recognized on Earth?
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What does the process of subduction involve?
What does the process of subduction involve?
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Study Notes
Earth's Moving Surface
- Earth's surface is broken into large, rigid pieces called tectonic plates
- These plates move relative to each other
- Plates are shown on a world map
- The plates, like puzzle pieces, are constantly moving
- The movement is very slow, but it has major effects
- Includes major plates (North American, Eurasian, Pacific, etc.) and minor plates
- Some plates are entirely oceanic crust and others are both oceanic and continental crust
Plate Boundaries
- Plate boundaries are identified by the relative motion of the plates as they move
- The types of plate boundaries are transform, divergent, and convergent
- Divergent boundaries occur where plates move apart, often creating new crust
- Convergent boundaries occur where plates move toward each other; one moves underneath another in a process called subduction
- Transform boundaries occur where plates slip past each other horizontally
Subduction Zone
- A subduction zone is the process that occurs when one tectonic plate moves under another tectonic plate
- It occurs at convergent boundaries
- The sinking part of the plate pulls the rest of the plate along
Plate Movement
- Tectonic plates move very slowly
- Measurements of the movement weren't possible until the mid-20th century due to the slow nature of the movement
- New technology, like GPS, can measure the position of locations on Earth precisely and track plate movements over time
- The average rate at which North America and Europe are separating is just 2.5 cm/year
- Scientists track plate positions to measure speed and direction of plate movement
Convection
- Convection is the circulation within fluids caused by differences in density and thermal energy
- The convection in the mantle can drag plates over Earth's surface
- Fluid heating unevenly causes warmer, less-dense fluid to rise, and cooler, denser fluid to sink. This constant motion is called convection
- Convection in the mantle drives plate motion
Density
- Density is the amount of matter per unit of volume
- Warmer fluids are less dense than cooler fluids
- Less dense fluid rises, denser fluid sinks
- This density difference contributes to tectonic plate motion
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