Geography tectonic plates Flashcards
how thick and how hot is the core?
Inner core: 1,400km,
Outer core: 2,100km,
Both are 3000-5000 degrees
why is the inner core solid?
because of the extreme pressure pushing the atoms together
Temperature range of mantle?
800-3000 degrees
parts of the mantle and its appearance?
lithosphere: rigid and brittle, floating on the asthenosphere
asthenosphere: it is very close to the rocks melting point, and very high in pressure, hence the rocks can be easily deformed
how do tectonic plates move?
Convection currents. The mantle material expands, rising and spreading beneath the plates, cause the plates to be dragged. The mantle cools and sinks pulling the plates along
what is slab pull force?
when a subducting, sinking oceanic plate at subduction zones pull the rest of the plate behind it
what is the main cause for plate movement?
Slab-pull force
why are transform plate boundaries bad?
Because it causes a build up of tremendous stress, to be released suddenly to cause devastating earthquakes
what are sedimentary rock?
Formed from multiple layers of sediment
what are igneous rocks?
Rocks that have cooled and solidifyed
what are metamorphic rocks?
When rocks are changed by high temperatures o pressure
Give 3 reasons why people may choose to live near a volcano.
Fertile soil, volcanic soil is rich in minerals. (Volcanic soils of Bali in Indonesia support cultivation of crops such as tea,)
Tourism, people enjoy the scenery. (Roman town of Pompeii, Italy was buried in layers of ash, 3 million people visit it annually)
Geothermal energy. Water comes into contact with hot rocks and evaporates, which is harnessed. (70% in Iceland are heated by volcanic steam)
What happens at transform plate boundary? Example of fault?
Plates slide past each other and get stuck. When pressure is released an earthquake occurs.
San Andreas fault
What can be created from convergent continental plate boundaries? How?
Fold mountains - continental crust is crumpled
Which is denser, oceanic or continental crust?
Oceanic
Oceanic oceanic plate divergence
when the plates diverge, fractures are formed at the plate boundary, allowing the magma to rise at the zone of divergence, creating a ridge of ocean floor called mid oceanic ridge
Magma rises at the zone of divergence, builds up and solidifying to form undersea volcanoes, which in turn rises above ocean level, forming volcanic islands
what happens in a continental continental plate divergence
The continental plates diverge, stretching and causing fractures to form at the plate boundary, where two scenarios can happen. Tensional forces could cause the central block of land could subside, resulting in a rift valley BETWEEN PARALLEL FAULTS. Creating a rift valley
Or the surrounding blocks of land could subside, causing a block mountain to form BETWEEN PARALLEL FAULTS.
what is a block mountain?
A block of land with steep slopes left standing higher than the surrounding land
Oceanic oceanic plate convergence
When they collide, the denser oceanic plate will subduct under the other plate, forming a oceanic trench (at the point of sunduction).
The subducting plate causes the plate above it to melt, allowing magma to rise through and form volcanoes
Earthquakes might occur due to friction between subducting plates
Continental continental plate convergence
the continental plates are too buoyant to subduct, so they compress. The compressional forces cause rocks to buckle and fold forming mountains
Oceanic continental plate convergence?
the oceanic plate subducts, causing a underwater (duh) trench to form at the point of subduction, while fold mountains are formed on the continental plate. The subducting plate causes the plate above it to melt, allowing magma to rise up and form volcanoes
small rocks that come out of the volcano during eruption
pryoclast
Low silica lava
not very viscous, form shield volcanoes, flows very fast
high silica lava
very viscous stratovolcano, flows very slowly
a reservoir of molten rock beneath the earth crust
magma chamber
vulcanicity
upward movement of magma into and onto earth’s surface
Example of shield volcano
Mount Washington in the united states of america
Example of stratovolcano
Mount Pinatubo in Philippines, in 1991
Pyroclastic flow
speed?
Pyroclasts that mix with super heated gas, so flying rocks mixed with gas,
40 metres per second
