Hazardous Earth: Tectonics Flashcards
What are the layers of the Earth?
Crust
Lithosphere
Upper mantle (asthenosphere)
Mantle
Outer core (liquid)
Inner core (solid, dense iron and nickel)
What are the properties of the inner core?
Solid ball made of iron and nickel.
It remains solid due to the huge amount of pressure of the whole Earth pushing against it.
Radioactive elements such as uranium and thorium are decaying - which gives off lost of heat.
Hot as the Sun - 6000°C
What are the properties of the outer core?
Molten layer of iron and nickel that surrounds the inner core.
Heat from the inner core creates convection currents in the outer core, which transfers heat to the mantle above.
What are the properties of the mantle?
The largest layer - mainly solid rock, apart from the asthenosphere which behaves like a highly viscous fluid (semi-molten rock).
The asthenosphere constantly moves due to convection currents, which move the solid lithosphere above.
3700°C near core, 1000°C near crust
What are the properties of the lithosphere?
Solid rock that lies on top of the asthenosphere. The majority of it is technically in the mantle, but the very top is the crust.
What are the properties of the crust?
Split into tectonic plates - range from tens to hundreds of km thick.
The crust is either continental (older less dense and thick) or oceanic ( younger, more dense and thinner).
Plates move due to movement of the liquid asthenosphere.
Describe the formation of convection currents
Radioactive decay in the core heats up the fluid asthenosphere. Hot liquid is less dense than cooler liquid, so it rises upwards and cools when it reaches the top. It becomes more dense again and sinks back to the bottom and this cycle continues.
The plates are pushed and pulled by these convection currents.
What are the 3 plate boundaries?
Divergent
Convergent
Conservative
What are divergent plate boundaries?
Plates which move away from each other.
Magma rises in the gap left by the two plates separating, then pours out into the surface (forming volcanoes). It cools and solidifies to form new land.
Lava is usually runny so forms flat, shield volcanoes.
Can occur on continental or oceanic crust (but not both together).
What natural hazards occur at divergent plate boundaries?
Earthquakes
Volcanic eruptions - non-explosive with low viscosity lava, creates shield volcanoes.
What are convergent plate boundaries?
Plates move towards each other.
It causes one of the plates to subduct into the mantle, where it is destroyed - usually, the denser oceanic plate is forced under the less dense continental plate where it melts to form magma, which causes pressure to build up in the crust. The magma is released in violent volcanic eruptions.
In two continental plates, neither can subduct below the other, so the crust is crumpled upwards by the building pressure, creating fold mountains.
What natural hazards occur at convergent plate boundaries?
Friction causes strong earthquakes.
Subducting plate leaves a deep ocean trench (not a hazard but whatevs)
Explosive volcano eruptions - where the melted magma pushes through weaknesses in the crust due to high pressure. Releases, hot gas, ash and rocks, and highly viscous lava, creating composite volcanoes?
What are conservative plate boundaries?
Plates move alongside each other.
Parallel plates move in different directions, this builds friction. Over many years the force of friction becomes so large that they eventually move in a sudden jolt, quickly releasing energy through the ground and causing an earthquake. This can also displace water in the ocean and cause tsunamis.
What natural hazards occur at conservative plate boundaries?
Earthquakes
Tsunamis
no volcanoes :’) - no new crust created or melted
What are hotspots?
Areas of volcanic activity where there are no plate boundaries. Hot magma plumes rise and burn through weaker parts of the crust, creating volcanoes and islands.
