Chapter 14 Flashcards
Continental Drift
Wegener’s hypothesis which suggested that continents are in constant motion on Earth’s surface
Pangaea
Name given to the super continent that began to break apart approximately 200 million years ago
Mid-ocean ridge
Long, narrow mountain range on the ocean floor; formed by magma at divergent plate boundaries
Normal Polarity
When magnetized objects, such as compass needles, orient themselves to point north
Magnetic reversal
An event that cause a magnetic field to reverse direction
Seafloor spreading
The process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away.
Reversed polarity
When magnetized objects reverse direction and orient themselves to point south
Plate tectonics
theory that Earth’s surface is broken into large, rigid pieces that move with respect to eachother
Lithosphere
The rigid outermost layer of Earth that includes the uppermost mantle and crust
Divergent plate boundaries
The boundary between two plates that move away from eachother
Transform plate boundaries
The boundary between two plates that slide past eachother
Convergent plate boundaries
The boundary between two plates that move towards eachother
Subduction
The process that occurs when on tectonic plate moves under another tectonic plate
Convection
The circulation of particles within a material caused by differences in thermal energy and density
Ridge push
The process that results when magma rises at a mid-ocean ridge and pushes oceanic plates in two different directions away from the ridge.
Slab pull
The process that results when a dense oceanic plate sinks beneath a more buoyant play along a subduction zone, pulling the rest of the plate that trails behind it.
Who came up with the theory of Pangaea and why couldn’t he prove it?
Alfred Wegener
He could not explain how the continents moved
What are four pieces of evidence to prove Pangaea-
thoroughly explain
Climate- Glacier grooves were found South America, Africa, India, and Australia where glaciers could not exist today.
Glacier sediments were also deposited in these continents.
Rock- Appalachian mountains match the same age, type, and geological structure of the Caledonian Mountains
Fossil- Glossopterius was found in South America, Africa, India,Australia, and Antarctica. Could not have traveled across the ocean.
who came up with the theory of seafloor spreading?
Harry Hess
What causes seafloor spreading
Plates separate at a divergent plate boundary, magma rises to the surface, cools, and pushes older crust apart.
Why is seafloor spreading a recycled process?
The older oceanic crust that the newly formed crust subducts underneath the continental crust. The older crust is heated into molten rock, magma, and can rise back up through the mid-ocean ridge.
Explain 2 pieces of evidence that supports seafloor spreading
The age of the crust and the magnetic reversal shown in the crust.
Where is the seafloor created? Destroyed?
It is created it the mid-ocean ridge when magma pushes up through it. It is destroyed at the subduction zone when in melts into magma.
If new seafloor is being created, why isn’t the Earth getting bigger?
As more is being created, the older crust is being destroyed. Both happen almost simultaneously.
How much do plates move?
A few centimeters each year, about 2.5.
What is a subduction zone?
the place where one tectonic plate moves under another more buoyant and less dense tectonic plate
What are the three plate boundaries?
Convergent, divergent, transform
How do the three different plates move?
convergent: —>
transform: —->
What forms at each boundary? .
Convergent:
oceanic/oceanic- trench, subduction zone, island arc
continental/continental- mountains
oceanic/continental- trench, subduction zone
Divergent:
oceanic/oceanic- mid-ocean ridge
continental/continental- rift valley, fault block mountains
Transform: earthquakes, ridge-like feature, looks like a scar.
Give examples of what forms at each boundary?
Convergent:
oceanic/oceanic- Marianas Trench, Marianas Islands
continental/continental- Himalyas Mountains
oceanic/continental- Cascadia mountain range
Divergent:
oceanic/oceanic- mid-atlantic ridge
continental/continental- Great rift valley in Africa
Transform: San Andreas Fault
Describe the crust
Thinnest layer of the earth- has two types:
oceanic- dense, made of basalt
continental- less dense, made of granite
Describe the mantle
Made of magma that is convecting, largest layer
Describe the outer core
Liquid iron and nickel that is hot and fast, creates the magnetic field
Describe the inner core
solid iron and nickel
What is the lithosphere and the astenosphere?
lithospere- upper mantle and crust
asthenosphere- lower mantle, molten rock
