Structure of Earth Flashcards
The first thoughts about continental drift were in?
1912 by Alfred Wegner
Alfred Wegner said that:
- South America fits Africa and therefore he suggested that continents are slowly drifting
- proposed an idea of historical single continent Pangea
Wegner did not have enough…
evidence and lack of a mechanism causing continental drift.
Later, American Harry…
Hess suggested that convection currents would force magma to well up in the interior and to crack the crust above and force it apart.
Further research in…
Mid Atlantic Ridge, showing sea-floor spreading supported the theory proposed by Hess.
In 1965 Wilson linked the ideas…
of continental drift and sea-floor spreading into a model of rigid plates and mobile belts-plate margins.
The evidence of plate tectonics:
- fit of continents
- glacial deposits in Brazil match those in West Africa
- the fossils in India match the fossils in Australia
The Earth is made up of…
a number of layers.
The temperature and…
density increases towards the core.
The continental crust:
- 35-70km thick
- older over 1500 million years
- lighter with an average density of 2.6
- granite and aluminium
The oceanic crust
- 6-10km thick
- under 200 million years old
- heavier with average density 3
- basalt and magnesium
The lithosphere is a layer…
that includes the Earth’s crust and the upper mantle.
The crust is cold…
and rigid and it can fracture.
The crust has a thickness around…
6km to 70 km,
The crust has the ability to glide…
over the rest of upper mantle.
