tectonics eq1 Flashcards
what does the earths structure consist of
crust, mantle, outer core, inner core
constructive boundary: oceanic and oceanic
Magma rises in between the gap left by the two plates separating, forming new land when it cools.
● Less explosive underwater volcanoes formed as magma rises.
● New land forming on the ocean floor by lava filling the gaps is known as sea floor spreading (as the floor spreads and gets wider).
constructive: continental and continental
Any land in the middle of the separation is forced apart, causing a rift valley.
● Volcanoes form where the magma rises.
● Eventually the gap will most likely fill with water and separate completely from the main island.
destructive plate boundary: continental and oceanic.
● Denser oceanic plate subducts below the continental.
● The plate subducting leaves a deep ocean trench.
● Built up pressure from the melting plate cause explosive volcanoes bursting through the continental plate.
destructive: oceanic and oceanic.
● Heavier plate subducts leaving an ocean trench.
● Built up pressure causes underwater volcanoes bursting through oceanic plate.
● Lava cools and creates new land called island arcs.
destructive: continental and continental.
● Both plates are not as dense as oceanic so lots of pressure builds.
● Ancient oceanic crust is subducted slightly, but there is no subduction of continental crust.
● Pile up of continental crust on top of lithosphere due to pressure between plates.
● Fold mountains formed from piles of continental crust.
what is ridge push
The slope created when plates move apart has gravity acting upon it as it is at a higher elevation. Gravity pushes the plates further away, widening the gap (as this movement is influenced by gravity, it is known as gravitational sliding).
what is slab pull
When a plate subducts, the plate sinking into the mantle pulls the rest of the plate (slab) with it, causing further subduction.
conservative plate boundary
Between any crust, the parallel plates move in different directions or at different speeds. No plates are destroyed so no landforms are created.
how do earthquakes happen at a constructive boundary
Plates move at different speeds, which builds pressure until plates crack, causing fault lines. This results in the release of energy in the form of seismic waves, producing earthquakes.
how do earthquakes happen at conservative boundaries
At a conservative boundary, plates lock with one another which, when pressure is built, produces sudden seismic waves.
how do earthquakes happen at a destructive boundary
one plate is forced under the other, getting stuck due to friction which produces energy. As plates suddenly jerk past one another, this energy is quickly released as large seismic waves, forming a powerful earthquake.
how are tsunamis formed
▪ Tsunamis are produced by sub-marine earthquakes at subduction zones, causing water displacement and deep trough waves.
▪ This hazard is always secondary to earthquakes. Tsunamis present additional damage to vulnerable communities.
▪ The movement of plates under the ocean causes an uplift of ocean water, disrupting the sea bed.
how do volcanoes form at a constructive boundary
magma is less dense than the plate so rises above it, forming a volcano, such as those within the Rift Valleys.
how do volcanoes form at a destructive boundary
subduction causes the melting of the oceanic plate, allowing for magma to rise on the crust to form a volcano. This produces explosive volcanoes such as Mt. St. Helens in the Ring of Fire.
define a disaster
A disaster is when a hazard affects human wellbeing. Degg’s Disaster Model suggests a disaster only happens when a hazardous event meets a vulnerable population.
define vulnerability
Vulnerability is how susceptible a population is to damage caused by a hazard. Resilience is how well a population can recover from a disaster
define a risk
A risk is the likelihood of humans being affected by a hazard. It is determined by the risk
equation:
Risk =
Hazard x V ulnerability Capacity To Cope
