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.
The lithosphere is the zone of…
earthquakes, volcanoes, mountain building and continental drift.
Moho discontinuity is a boundary…
which divides the upper mantle from the crust.
At the Moho discontinuity the seismic waves from…
earthquakes travel faster indicating the change in the structure=the transition zone between the mantle and crust
The mantel has thickness almost…
2900km
The upper mantle is located from the base…
of crust downwards to a depth of about 670km.
The asthenosphere is the top…
layer of the upper mantle. Thick around 100-200km
The asthenosphere has physical properties that are…
different from the rest of the upper mantle. The rocks are more rigid and brittle due to lower temperatures, but still deform slowly and floats.
The mesosphere is the layer under…
the asthenosphere, made of a lower layer of upper mantle and the lower mantle.
The lower mantle extends from…
670km to 2900km. It has a temperature of about 1000 degrees.
The lower mantle has plastic…
like properties that enable it to flow and it is made of lower density material=periodite.
The core has a diameter around…
7000km.
The inner core is…
solid made of nickel and iron.
The outer core is molten…
iron.
Movements in the outer core are thought to be responsible for…
earth’s magnetic field.
The inner core is under extreme…
pressure that despite being hot (6000) it is solid up to 5 times denser than the surface rock.
