-
Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have
enough elevation to extend above sea level.
-
The ridge is a slow spreading center and has an average spreading rate of about 2.5
centimetres (0.98
in) per year and forms an ocean trench about the size of the Grand
Canyon.
General classification and sub-classification of igneous rocks
Categories of rocks
-
Felsic (most silica rich)
o
Granite (coarse-grained)
-
Intermediate
o
Diorite (coarse-grained)
o
Andesite (fine-grained)
-
Mafic
o
Gabbro (coarse-grained)
o
Basalt (fine-grained)
-
Ultra-mafic (most Fe+magnesium rich)
o
Peridotite (coarse-grained, typically subcrustal)
The major elements and minerals that make up the crust, mantle and Earth as a whole
Earths mass
-
Comprises of: iron (32%), oxygen (30%), silicon (15%), magnesium (14%)
-
The remaining of Earth’s mass consists of the remaining 88 elements
Elements in Earth’s crust – all approximate amounts
-
47% oxygen
-
28% silicon
-
8% aluminum
-
5% iron
-
4% calcium
-
3% sodium
-
3% potassium
-
2% magnesium
Earth’s mantle
-
Upper mantle
o
Inner zone: plastic flowing rock
o
Outer zone: rigid rock
-
Elements in the mantle:
o
45% oxygen
o
22% silicon
o
23% magnesium
o
Iron. Aluminum, calcium, sodium, potassium
o
These elements are all bound together in the form of silicate rocks
Earth’s materials
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