Earth Science B Chapter 10
According to Wegener, how did continents move?
Continents plowed through rock on ocean floor (this was disproved)
What deep-ocean feature forms a subduction zones
Deep-ocean trenches
Oceanic crust
Dense crust made of rock that is rich in iron and magnesium
Slab pull
The force exerted buy a sinking plate caused by the subduction of lithosphere into the asthenosphere
Ridge pushing
The force on the rest of the plate from the asthenosphere below cooling sinking rock
rifting
The process by which a continent breaks apart
accretion
The process by which a terrane becomes part of a continent
Compared to sediment found farther from a ridge, sea-floor sediment closer to a ridge is
thinner
Compared to rocks farther from a ridge, rocks closer to a ridge are
younger
rift
A crack in Earths crust
Sea-floor spreading
A mechanism that causes the continents to move and verifies Wagener hypothesis of continental drift is
Rift valley
A narrow area that forms where the plates at a divergent boundary separate (i.e Red Sea)
terrane
A piece of lithosphere that has a unique geologic history
atoll
A small coral island
seamount
A small volcanic island of underwater mountain
earthquakes
A sudden movement along the boundary of a tectonic plate
Pacific Ring of Fire
A zone of active volcanoes and earthquakes the encircles the Pacific Ocean
How many major tectonic plates have scientists identified
About 15
Where does new rock form on the sea floor
At the rift in a mid-ocean ridge
Tectonic plates
Blocks of earths shell that ride on a deformable layer of the mantle
divergent
Boundary between tectonic plates that are moving away from each other
transform
Boundary between tectonic plates that are sliding past each other horizontally
How do Continents move over earths surface
By the widening sea floor, which acts as a conveyor belt
Island arc
Chain of volcanic islands
How are transform boundaries different from other types of boundaries
Don't produce magma (i.e San Andreas Fault)
Where were the older rocks on the sea floor
Farther away on either side of the ridge
Most of earths continental surfaces were once covered by
Ice (all continents were located near the south pole)
cratons
Large areas of stable rock older than 540 million years
Supercontinent
Large landmasses formed in the past from smaller continents
Continental crust
Low-density crust made of rock that is rich in silica
magma
Molten rock
Continental Drift
Movement of continents that are located on separate tectonic plates.
Supercontinent form when
New convergent boundaries form after continents collide
Rocks with magnetic fields that point north have
Normal polarity
subduction zone
Region where one plate moves under another
Rocks with magnetic fields that point south have
Reversed polarity
Scientists have found evidence of reversal patterns in
Rocks on the ocean floor and on land
shield
Rocks that have been exposed at earths surface
Fracture zone
Short segments of a mid-ocean ridge that are connected by transform boundaries
"plastic" rock
Solid rock under great pressure that flows slowly, like putty
asthenosphere
Solid, plastic layer of the mantle beneath the lithosphere
How do scientists identify plate boundaries
Studying data from earthquakes
What did Wegener hypothesize about mountain ranges ?
That the crumpling of the crust in places produced them
Pangaea
The Supercontinent that formed about 300 million years ago
The Tethys Sea
The body of water on the eastern edge of pangaea (eventually became the Mediterranean Sea)
convergent
The boundary between tectonic plates that are colliding
Where were the youngest rocks on the sea floor
The center of the ridge
Convection cell
The cycle in which the cooler, denser water sinks and the warmer water rises to the surface to create a cycle
lithosphere
The solid outer layer of earth, that consists of the crust and the rigid upper apart of the mantle
paleomagnetism
The study of the magnetic properties of rocks
Plate tectonics
The theory that explains why an how continents move
Fracture zones
Transform boundaries that connect short segments of a mid-ocean ridge
Mid-ocean ridge
Undersea mountain range
Mid-ocean ridges
Undersea mountain ranges with steep, narrow valleys in the center are called
Compared to speed of plates that are not subduction, plates that are subduction move
faster
