Structure of Earth Flashcards
Describe the actual structure of earth
Geoid - bulges round equator flatter at poles. Not perfect sphere
= centrifugal forces generated earth rotation
Which flings semi molten interior outward
-inner core
- outer core
- mantle
- crust
Describe characteristics of earth crust
5-70 km thick
Brittle
Earth outer shell -we live on
2 types oceanic and continental
What are continental shelves
Edge of continent lies under sea
- shallow seabed close to shore
Within oceanic plate there is sima. What layer of crust is this and what occurs at it?
Lowest level earths crust
Beneath oceans and grading into lowest part of sial beneath continents
How do flood basaltic eruptions occur?
At oceanic crust result of erupted mantle material from below plate
This is cooled and modified chemically by sea water
This happens at mid ocean ridges + scattered hot spot.
What is the asthenosphere?
What are the properties?
The upper mantle layer of earth.
Semi molten approx 2000 km wide
Moves slow carrying lithosphere on top.
Malleable and lubricating underside crustal plate.
What occurs due to phenomenal heat at core
Convection currents within mantle, spread very slowly within asthenosphere.
Define magma
Molten rock
G + L from mantle accumulating vast chambers at great pressure deep within lithosphere
Surface magma is lava
Define ignores rock
Rock formed due to cooling of molten magma
Either on ground surf (extrusive) or underground (intrusive)
What is the difference between intuitive and extrusive
Intuitive - magma cools, crystallises and solidifies slowly below surf
= corse grained igneous rock eg granite and dolrite
Erosion removes underlying rocks = vertical dyke and horizontal inclined sills
Extrusive - lava in contact air or sea
Cools, crystallises, solidify
= igneous rock
Eg. Basalt (fined grained small crystals)
