geography unit three Flashcards
plate tectonics
The theory that Earth’s outer shell is made up of individual plates that move, causing earthquakes, volcanoes, mountains and the formation and destruction of areas of the crust.
plates
Plates are different pieces of crust that float around on molten rocks inside the Earth.
subduction
The process in which one plate slides underneath another. The subducted plate moves into Earth’s interior and is “recycled” (it melts).
mid-ocean ridge
A feature created by the spreading of the sea floor where two plates are diverging. The best known example runs through the Atlantic Ocean from north to south.
continental plate
Continental plates are rocks that are less dense than oceanic plates moving above those plates forming land masses such as eurasia and africa. When two continental plates collapse, they form natural land masses such as mountains.
oceanic plate
Oceanic plates are more dense rocks that make up continental plates which slide underneath continental plates.
divergent plates
This occurs when two plates move apart. Most commonly this happens along a mid-ocean ridge, although it does happen on land too. When this happens both plates get larger. New areas of Earth’s crust are constantly being created.
convergent plates
Two plates moving towards each other. There are two types of convergence depending on the kinds of plates that are colliding.
The two types of convergence
Continental plate meets oceanic plate:
The rocks that make up deep-ocean plates that are more denser make continental plates. This is called subduction. The crust melted here balances the new crust forming at a divergent plate boundary. When the pressure builds up for centuries there are 8.0-9+ earthquakes
Continental plate meets continental plate
When two continental plates run into each other, massive layers of rock are folded,broken, and forced upward by the immense pressure of the collision. This created mountains.
transforming plates
Along a transform boundary (also called a conservative plate boundary), plates are made neither larger nor smaller. In these locations, plates move roughly parallel, but in opposite directions. This process often happens fairly smoothly with many small earthquakes. Sometimes plates lock up for many years until a enormous release of energy occurs, ranging from 5.5-7.5
In which region of Canada do volcanic mountains exist
Western Canada
When was the last eruption in Canada
Canada’s most recent eruption was 150 years ago at Lava Fork Volcano in northwestern B.C
Cinder cone volcano
When runny lava contains less gas, the volcano erupts in rivers while sloping down and form a hill.
Shield volcano
If lava is vicious rather than runny, gases will not escape. Vicious lava with little trapped gas will pile up in steep sided domes.
Stratovolcano
Vicious lava with a lot of trapped gas will erupt explosively, spreading ash over wide areas.
what are the greatest volcanic hazard is ________ ash from distant volcanoes, what problems can this cause?
wind-borne
a) Contamination of water b) Threaten the health of people
c)Damage Crops d) Pose a threat to aircraft
Crust Characteristics
-Makes up less than 1% of Earth’s mass
-5-70km Thick
-Solid and Brittle
-Oceanic crust (under water)
-Continental Crust (land mountains)
Mantle characteristics
-2,900 kilometres thick
-64% of the Earth’s mass
-Layer of the Earth between the crust and the core (upper and lower mantle)
- Made of Moltern rocks of medium density
-Molten, solid-semi rock
-Magma (under the crust), lava (outside the crust)
Outer Core characteristics
-2,200 kilometres thick
-Outer shell of Earth’s core
-Made of Liquid nickel and iron
Inner Core characteristics
-Sphere of solid nickel and iron at the centre of the earth.
-1228 kilometre radius
- Temperature in the core is hotter than the surface of the sun (as hot as 4000-6000 degrees celsius)
-This intense heat from the inner core causes material in the outer core and mantle to move around.
What causes the plates to move?
Convection currents - circular movement in a gas or liquid created by unequal heating
Wearing Down:
Agents such as water, ice, and wind act to wear down the surface of the Earth
What is an example of wearing down?
Ex. Young mountains have experienced little weathering and erosion
Older mountains have experienced much weathering and erosion
Weathering:
The breaking down of rocks into smaller pieces (sediment). Entire mountains can be weathered into sediment by wind, water or chemicals
Erosion:
the picking-up and movement of weathered rock particles (sediment) by wind or water
River erosion:
Moving water picks up the sediment and deposits them down river
Deposition:
the layering down of sediment in a new location. Usually happens when wind or water carrying sediment slows down
