Hazardous Earth Flashcards
What are the main layers of the Earth?
The main layers are: the crust, the mantle, the outer core, and the inner core.
What are the features of the crust?
The crust is the thinnest layer, it is 50km to 100km thick. It consists of several tectonic plates which are moved by the mantle.
What are the features of the mantle?
The mantle is 2900km thick, it consists of the upper mantle and the lower mantle. The upper mantle consists of the lithosphere and the asthenosphere. The lithosphere is viscous while the asthenosphere is less mobile and more solid.
What are the features of the outer core?
The outer core is at a temperature of 4000 °C to 5200 °C. It is around 2200km thick. It is made up of liquid iron and nickel and has a magnetic current.
What are the features of the inner core?
The inner core is 1200km thick, it is made of mostly solid alloy of iron and nickel, and it is slowly growing.
What is the difference between oceanic and continental crust?
The continental crust forms the land. This is made mostly of granite, which is a low density igneous rock. It is on average 30-50km thick.
Under the oceans is oceanic crust. This is much thinner, usually 6-8km thick. It is also denser and made of an igneous rock called basalt.
How do we know that it is hot inside the Earth?
We know it’s hot because of molten lava spewing from active volcanoes, and because of hot springs and geysers.
Why is the inside of the Earth hot?
The inside of the Earth is hot due to radioactive decay. Radioactive decay is when unstable atoms release particles from their nuclei, creating heat.
Why do tectonic plates move?
Tectonic plates move due to convection currents in the mantle, created by heat rising from the core.
What are the different types of plate boundaries?
Divergent - where two plates are pulled apart.
Convergent - where two plates are pushed together.
Conservative - when two plates slide past each other.
Collision - where one plate is forced under the other.
How is new oceanic crust formed?
New oceanic crust forms at divergent plate boundaries. Convection currents bring magma up from the mantle, this mantle is then injected between the separating plates. As the magma cools, it forms new oceanic crust. The plates then continue to move apart, allowing more magma to be injected.
What is subduction?
Subduction describes oceanic crust sinking into the mantle at a convergent plate boundary. As the crust subduction, it melts back into the mantle.
What are collision zones?
Collision zones are a type of convergent boundary. They form mountain ranges like the Himalayas. Two continental plates of low-density granite collide, pushing up mountains. Earthquakes happen on faults in collision zones.
What are faults?
Faults are huge cracks in the Earth’s crust.
Which tectonic hazards occur at conservative plate boundaries?
- Destructive earthquakes up to magnitude 8.5.
- Small earth tremors almost daily.
