The Structure of the Earth Flashcards
Describe the structure of the Earth
A sphere with a thin rocky crust, mantle and core.
What is the middle of the earth made of?
The core contains iron
What causes volcanoes and earthquakes?
The movement of the tectonic plates.
How fast do plates move?
About 2.5 cm a year.
What happens if you add up all the plate movements over millions of years?
You get continental drift; the continents move around very slowly, India was once part of Africa.
What theory is now used for plate movements?
Plate tectonics is now widely accepted by scientists.
Describe the outer layer of the Earth
Oceanic plates under oceans, continental plates under continents.
What is the lithosphere?
The cold hard bit at the surface, the crust and the top of the mantle.
Why do plates float?
Why do plates float?
Why is studying the Earth’s structure difficult?
We can only drill so far in; the rest is based on seismology, the study of sound waves in the rock that are caused by explosions or earthquakes.
Why is plate tectonics now a widely accepted theory?
It explains a wide range of evidence; it has been discussed/ tested by a wide range of scientists.
Describe the mantle.
The bit between the crust and the core, a semi-solid that is hotter and runnier at the bottom.
What provides the energy for plate tectonics?
Radioactive processes in the core give heat to the mantle. Convection currents then cause the plates to move slowly.
When plates meet, what goes where?
Oceanic plates are more dense than continental so in destructive collisions there is subduction and partial re-melting of the oceanic plates.
At the ocean margins, what goes where?
Plates are cooler at ocean margins and so they sink and pull plates down.
