Chapter 2 Flashcards
Lithosphere
Earths crust and uppermost part of the layer below (mantle) form the lithosphere
Extends to 100-150 km
Lithosphere plates
The lithosphere is not a single shell , but consists of several large pieces also know just as plates
There are 12 major plates and several minor plates
Continental lithosphere
Is thicker than oceanic lithosphere
Asthenosphere
What the plates rest on
A zone in the upper mantle (jelly-like solid)
Allows plates to move
Divergent boundaries
(Ocean ridges)
New lithosphere is created from molten material rising from asthenosphere
Plates move away at the axis of Submarine mountain ranges called mid-ocean ridges
Convergent boundaries
(Subduction zones or areas of continent-continent-collision)
Old lithosphere is destroyed
one plate sinks into the mantle below the other in subduction zones
creates trenches (places between the two plates)
Transform faults
(Neutral plate boundaries)
Lithosphere is neither created nor destroyed
slide past one another along vertical zone of fracturing called a transform fault
Most break ocean ridges into segments
Plate boundary
Place where two plates make contact
Triple junction
Where three plates come together
Sea floor spreading
Ocean becomes wider through this process where new lithosphere moves outward from the axis to the flanks of the ridge
Theory of plate tectonics
Plate tectonics explains the outer layer of the earth as a group of separate plates that move with respect to each other and change the Earth’s surface as they move
volcanic islands
on convergent plate boundaries where the overriding plate is made of oceanic lithosphere
continental arc
on convergent plate boundary like the Andes Mountains where the overriding plate is made of continental lithosphere
continental collision
when subduction completely consumes an oceanic plate between two continents and forms a collisional mountain belt
Continental rifts
places where continental lithosphere is stretched and pulled apart in the process of breaking apart at a new divergent margin. if successful, a continent splits into two pieces separated by a new oceanic plate, which gradually widens by seafloor spreading.
tectonic cycle
new oceanic lithosphere is created at the ocean ridges, moves away from the ridges during seafloor spreading, and returns to the mantle in subduction zones.
Principle of uniformitarianism
ancient salt deposits, reefs, and glacial deposits should have formed in locations similar to those where they form today
Ring of Fire
surrounding the Pacific Ocean
Most volcanoes are concentrated in narrow belts near the edges of continents
paleomagnetism
some rocks that contain magnetite or hematite therefor preserve a weak record of Earth’s ancient magnetic field
reverse polarity
a compass needle that points to today’s north magnetic pole would swing around and point south
hotspots
an area of unusual volcanic activity not associated with processes at plate boundaries.
mantle plume
a column of very hot rock that rises by slow plastic flow from deep in the mantle.
seamounts
when old volcanoes sink below the ocean surface
active continental margin
where earthquakes and volcanic eruptions are common
passive continental margin
where earthquakes and volcanic eruptions are rare.
