Physical Geology Test 4 Chapter 15

Front 1

Plate Tectonics

Back 1

“The theory that proposes Earth’s outer shell consists of individual plates, which interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself”.

Front 2

Continental Drift

Back 2

“A hypothesis, credited largely to Alfred Wegener, which suggested all present continents once existed as a single supercontinent. Further, beginning about 200 million years ago, the supercontinent began breaking into smaller continents, which then drifted to their present positions”.

Front 3

Pangea

Back 3

“The proposed super continent that 200 million years ago began to break apart and form the present landmasses”.
Wegener argued that some process must explain the similar fossil records on widely separated landmasses.

Front 4

Plates

Back 4

“One of numerous rigid sections of the lithosphere that moves as a unit over the material of the asthenosphere”.

Front 5

Divergent plate boundaries

Back 5

where plates move apart, resulting in the upwelling of material from the mantle to create new seafloor

Front 6

convergent plate boundaries

Back 6

Where plates move together, resulting in the subduction of oceanic lithosphere into the mantle. 3 kinds

Front 7

Transform fault boundaries

Back 7

Where plates grind past each other without the production or destruction of the lithosphere.

Front 8

Subduction Zones

Back 8

 The area where an oceanic plate descends into the asthenosphere is called a subduction zone.

Front 9

Volcanic Island Arc

Back 9

 The volcanic activity produces an arc-shaped chain of small volcanoes called volcanic island arcs (i.e. Aleutian, Mariana, and Tonga Islands) Oceanic-Oceanic

Front 10

Continental Volcanic Arc

Back 10

 Volcanic activity produced by the subduction of the oceanic lithosphere can create mountains termed continental volcanic arcs (i.e. the Andes Mountains, the Cascade Range). Oceanic-Continental

Front 11

Oceanic-Continental

Back 11

When these two plates converge, denser oceanic lithosphere sinks into the asthenosphere below the less dense continental lithosphere.
Volcanic activity produced by the subduction of the oceanic lithosphere can create mountains termed continental volcanic arcs (i.e. the Andes Mountains, the Cascade Range).

Front 12

Oceanic-Oceanic

Back 12

When two oceanic lithospheric plates converge, one descends beneath the other creating volcanic activity similar to that observed in oceanic-continental convergence.
However, this volcanic activity produces volcanoes on the ocean floor rather than on a continent
The volcanic activity produces an arc-shaped chain of small volcanoes called volcanic island arcs (i.e. Aleutian, Mariana, and Tonga Islands)

Front 13

Continental-Continental

Back 13

When two continental lithospheric plates converge, neither plate will subduct beneath the other due to the buoyancy and low density of the material.
This results in the buckling, fracturing, shortening, and thickening of the continental lithospheric plate.
The most famous example of this occurrence is the Himalayan Mountains
Other examples include the Alps, Appalachian, and Ural mountains.

Front 14

Crust

Back 14

Comparatively thin outer skin that ranges from 3 kilometers (2 miles) at the oceanic ridges to 70 (40 miles) in some mountain belts.
Thinnest layer, less dense than any other layer
Two types: Oceanic and Continental
Continental: thicker, less dense, composed mainly of oxygen, silicon and aluminum (granitic).
Oceanic: thinner, more dense, mainly composed of basalt (iron rich)

Front 15

Mantle

Back 15

a solid rocky (relatively silica rich) shell that extends to a depth of about 2900 kilometers (1800 miles)
83% of Earth’s volume. Solid layer beneath the earth’s crust tht moves in slow convection currents, distributing the internal heat of the earth. Made of iron and magnesium silicates.

Front 16

Core

Back 16

An iron rich sphere having a radius of 3486 kilometers (2161 miles)
Innermost layer, composed mainly of iron and nickel. Consists of a liquid outer core and a solid inner core. Causes Earth’s magnetism.

Front 17

Lithosphere

Back 17

cool, rigid outer layer. Made of crust and uppermost mantle. Extends to an average depth of 100 km. Makes up the plates of plate tectonics.

Front 18

Asthenosphere

Back 18

Hot, plastic layer of upper mantle beneath lithosphere. This layer is “slick” when force is applied slowly, and allows plates to slide over it.
To a depth of 660 kilometers (depth at which earthquakes stop happening)
Small amount of melting in the upper portion mechanically detaches the lithosphere from the layer below allowing the lithosphere to move independently of the asthenosphere.

Front 19

Lower Mantle/Mesosphere

Back 19

Rigid
660-2900 kilometers
Rocks are very hot and capable of very gradual flow

Front 20

Outer Core

Back 20

Liquid
Composed mostly of iron-nickel alloy
1410 miles (2270 kilometers) thick
Connective flow within generates Earth’s magnetic field

Front 21

Inner Core

Back 21

Solid
Sphere with a radius of 1216 kilometers (730 miles)
Material is stronger than the outer core.