Composition of the earth

Question 1

What is the homogenous model of accretion?

Answer 1

• The Earth was formed by a homogeneous composition
• The Earth began to warm due to radioactive decay
• The melting process began at shallow depths because more pressure requires more heat to melt
• Heavy metals began to migrate to the center until it was full of Ne and Fe.
• Lighter elements such as Na, Ca, K, Al concentrated near the surface.

Question 2

What are the four types of meteorites

Answer 2

1) Iron meteorites
2) Stony-Iron meteorites
3) Stony Chondrite meteorites - Formed far away in belt
4) Stony achondrite meteorites - From terrestrial body (contains igneous rock)

Question 3

What is the density of Earth

Answer 3

Earth is the Densest planet in the solar system

Density = 5.52 g/cm3

Question 4

How much of the mass of the solar system is contained in the sun

Answer 4

99.8%

Question 5

What is the percentage of different types of meteorite that hit the earth?

Answer 5

61% - Stony (84% Chondrite, 8% Achondrite)

35% - Iron

4% - Iron/Rocky

Question 6

What is the composition of Chondrites?

Answer 6

• Many contain chondrules (small 1mm spheres of 40% olivine and 30% pyroxene)
• Some of them have inclusions of calcium which date back to the first condensations of the solar system

Question 7

What is the composition of Achondrites?

Answer 7

• No chondrules, similar to earth rocks

- Rich in Olivine, basalts, peridotite

Question 8

What is peridotite?

Answer 8

A dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultra-magic with less than 45% silica. Derived from the earth’s mantle.

Question 9

What is a siderito?

Answer 9

an iron meteorite

Question 10

What is a volatile element?

Answer 10

(Na, P, C, K, Rb, etc.) elements with low boiling temps.

Question 11

What is a refractory element?

Answer 11

Non volatile elements (high condensation temp) (Mg, Al, Si, Ca, Ti, Th, U, etc.)

Question 12

What is a siderophile element?

Answer 12

High density transition metals (Gold, cobalt, Iron, Iridium, etc..)

Question 13

What is a chalcophile element?

Answer 13

Transition metals (silver, etc) that like to bond with sulfur.

Question 14

What is a lithophile element?

Answer 14

Elements that tend to bond with oxygen in oxides and silicates (K, Na, Mg, etc)

Question 15

What are major elements?

Answer 15

Hydrogen and Helium

Question 16

What are minor elements?

Answer 16

Li, Be, and B (Very low amounts)

Question 17

What are trace elements

Answer 17

An element that is less than 0.1% of the composition

Question 18

What are compatible and incompatible trace elements?

Answer 18

Incompatible are high in the crust and low in the mantle (Uridium, Barium, Uranium, etc), Compatible are high in the mantle and low in the crust (Nickel, Titanium). If an element is incompatible it partitions into a melt as soon as melting begins.

Question 19

16) What are the differences in the composition of the earth and the moon?

Answer 19

The moon’s surface is made up of basalt and anorthsite (uncommon on earth). The moon’s surface is much older than the earth.

Question 20

What were the first materials to condense?

Answer 20

Because iron has a higher melting temperature and condensation temperature it would be on of the first to condense in a gas cloud. Next would be the silicates which would condense around the core, and finally the volatile elements would condense and form the crust. Experimental data shows that the first elements to solidify were rich in Ca, Al, and Ti followed by Fe, Ni, and Mg rich silicates.

Question 21

Describe the model of homogenous accretion

Answer 21

The earth formed in more or less a uniform material of large amounts of iron but mostly of silicate material. Fusion began at lower depths initially because more heat is needed at higher pressures. Eventually from heating (radioactive decay, and other sources) the center became liquid until heavier elements were able to concentrate in the center and form the core.