C2a-structure Of The Earth Flashcards
What is the lithosphere?
The cold rigid outer part of the earth that includes the crust and part of the mantle
Made of tectonic plates that are less dense than the mantle below
What are the problems associated with studying the structure of the earth?
Crust is too thick to drill through
Need to use seismic waves produced by earthquakes or man made explosions
Why is the theory of plate tectonics now widely accepted?
Explains a wide range of evidence
Discussed and tested by a wide range of scientists
New evidence of sea floor spreading 1960
Subsequent research supported theory
What is the mantle?
Zone between the crust and the core
Cold and rigid just below crust
Hot and non rigid at greater depths, able to move
What is the theory of plate tectonics?
- energy transfer involving convection currents in the semi rigid mantle causing plates to move slowly
- Oceanic crust more dense than continental crust
- collision between Oceanic plate and continental plate leads to subduction and partial melting
- plates cooler at ocean margins so sink and pull plates down
What is theory that 300 mil years ago there was one supercontinent which broke into smaller chunks called?
Alfred wegeners continental drift theory 1914
Why wasn’t the continental drift theory accepted at that time?
His explanation of how drifting happened wasn’t convincing
Movement wasn’t detectable
Geologists showed tidal forces and earths rotation didn’t cause movement
What is magma?
Molten rock beneath the surface of the earth
What is lava?
Molten rock at the earths surface
How is igneous rock made?
When any sort of molten rock cools down and solidifies
How is iron rich basalt formed?
Fairly safe volcanic eruption
Runny lava
Cools quickly
Small crystals
How is silica rich rhyolite formed?
An explosive eruption
Thick lava
Cools slowly
Large crystals
What are the layers of the earth?
Sphere Thin rocky crust Mantle Liquid outer core Solid iron inner core
Why do some people choose to live near a volcano?
Volcanic ash creates very fertile soil great for farming
Why do geologists study volcanoes?
To be able to forecast future eruptions
To reveal information about the structure of the earth
