Chapter 22 Tectonic Plates
What is a plume?
a zone of upwelling material originating at the outer core-mantle boundary
The hypothesis of continental drift was supported by the jigsaw fit of the continents, similar _______.
fossils, matching rock types, and ancient ice sheets
The core of Earth is probably composed of
iron and nickel
Outer core
the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core
According to the theory of seafloor spreading, large quantities of molten rock rises up along
the mid-ocean ridges.
Midocean ridge
A global system of underwater mountains created by seafloor spreading
Plate Tectonics
A theory stating that the earth's surface is broken into plates that move.
Which of the following mountain ranges are examples of continental arcs?
Andes and Cascades
Ocean Trench
Deep valley in the ocean floor that forms along a subduction zone
Lower mantle
One of Earths structural layers---the lowest portion of the mantle, a zone of strong, rigid rock.
Asthenosphere
One of earths structural layers-----a layer of weak, warm rock that flows slowly over geologic time.
Inner core
One of the Earth's structural layers---a solid sphere of hot metal, most iron, at the center of the earth.
Transform boundaries
Places where tectonic plates slide along beside one another as they move
How do plates move at divergent plate boundaries?
Plates move apart.
What is the relationship between the crust and lithosphere?
The crust is part of the lithosphere.
Differentiation
The process by which earth formed layers according to density
Subduction
The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
Seafloor spreading
The process that creates new sea floor as plates move away from each other at the mid-ocean ridges
Subduction zone
The region where oceanic plates sink down into the asthenosphere.
Earthquake
The shacking of the ground that results when rock under Earth's surface moves or breaks.
Earth Science
The study of history, structure, and natural processes of planet earth
Mantle
The thick layer of dense, hot rock between Earth's crust and core.
Why do we say that Earth science is an integrated science?
Earth science encompasses a broad spectrum of natural science disciplines, including physics, chemistry, biology, and astronomy.
What features at the surface provide evidence of plumes?
Hot spots
What is the relationship between temperature and density?
In general, warmer materials are less dense, and colder materials are denser.
Tectonic plates
Large movable plates under the Earth's surface.
Magma
Molten rock beneath the earth's surface
Why are volcanoes NOT found at transform boundaries?
Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.
What is convection?
a cycle of moving material formed by the rise of less-dense material and the sinking of denser material
What is a volcanic arc?
a row of volcanoes that forms on the overriding plate near a subduction zone
Transform faults are areas of crustal
accommodation and plate movement
Convergent boundaries are
all of the above
Where is the youngest ocean floor found?
along the crest of mid-ocean ridges
The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?
an ocean
The mantle can be separated into two different portions-the lower mantle and the upper mantle. The lower mantle is
completely solid due to extreme pressure that prevents rocks from melting.
Continental crust extends farther down into the mantle than oceanic crust because
continental crust is thicker than oceanic crust.
Divergent boundaries are areas of
crustal formation.
Which of the following terms best characterizes upwelling in the asthenosphere?
diffuse
In general, where do earthquakes AND volcanic eruptions occur?
divergent plate boundaries convergent plate boundaries
Plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.
divergent/convergent/transform
Alfred Wegener supported his theory of continental drift by
making a connection between the rocks, rock structures, and plant and animal fossils found in both Africa and South America.
Which geologic features are associated with divergent boundaries?
mid-ocean ridges and continental rift valleys
What forms at divergent plate boundaries?
new oceanic lithosphere
Which geologic features are associated with convergent boundaries?
ocean trenches and volcanoes
The two elements that make up about 75% of Earth's crust are__________ and________.
silicon and carbon
Isostasy is
the positioning of the crust in response to the buoyant force and gravity. (equilibrium)
What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?
The Earth would increase in volume.
What accounts for most tectonic plate motion?
forces at subduction zones
Seafloor spreading provides the mechanism for continental drift, because at the spreading center _______.
formation of new lithosphere pushes the continents
Because S-waves do not travel through Earth's outer core, scientists inferred that the outer core is
molten liquid.
Complete this statement: Divergence is to moving away as convergence is to _______.
moving toward
The three kinds of plate convergence are
oceanic-oceanic continental-oceanic continental-continental
In general, where do volcanoes form in subduction zones?
on the overriding plate, away form the convergent boundary
The theory of seafloor spreading is supported by
paleomagnetic analysis of the ocean's floor.
Convergent boundaries
place where two plates come together
How do plates move at transform plate boundaries?
plates move side by side
How do plates move at convergent plate boundaries?
plates move toward one another
The inner core is solid because
pressure from the weight of the surrounding layers prevents the inner core from melting
P-waves refract at the boundary between inner and outer core because
there is a change of phase between inner and outer core
The theory of plate tectonics states that the continents move because _______.
they are embedded within the drifting lithospheric plates.
Lithosphere
Earth's outermost structural layer, consisting of cool, rigid rock
Crust
Earth's surface layer, consisting of oceanic and continental crust
Core
Earths innermost layer, which is mostly iron and includes the inner core and outer core
Divergent boundaries
Places where plates are pulling apart
Continental drift
The hypothesis that the continents slowly move across Earth's surface.
Oceanic and continental crust differ in that
All of the above.
Geology
The Earth science that is concerned with the composition and structure of the Earth.
Seismology
The study of earthquakes