Composition of the earth Flashcards
(21 cards)
What is the homogenous model of accretion?
- 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.
What are the four types of meteorites
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)
What is the density of Earth
Earth is the Densest planet in the solar system
Density = 5.52 g/cm3
How much of the mass of the solar system is contained in the sun
99.8%
What is the percentage of different types of meteorite that hit the earth?
61% - Stony (84% Chondrite, 8% Achondrite)
35% - Iron
4% - Iron/Rocky
What is the composition of Chondrites?
- 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
What is the composition of Achondrites?
- No chondrules, similar to earth rocks
- Rich in Olivine, basalts, peridotite
What is peridotite?
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.
What is a siderito?
an iron meteorite
What is a volatile element?
(Na, P, C, K, Rb, etc.) elements with low boiling temps.
What is a refractory element?
Non volatile elements (high condensation temp) (Mg, Al, Si, Ca, Ti, Th, U, etc.)
What is a siderophile element?
High density transition metals (Gold, cobalt, Iron, Iridium, etc..)
What is a chalcophile element?
Transition metals (silver, etc) that like to bond with sulfur.
What is a lithophile element?
Elements that tend to bond with oxygen in oxides and silicates (K, Na, Mg, etc)
What are major elements?
Hydrogen and Helium
What are minor elements?
Li, Be, and B (Very low amounts)
What are trace elements
An element that is less than 0.1% of the composition
What are compatible and incompatible trace elements?
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.
16) What are the differences in the composition of the earth and the moon?
The moon’s surface is made up of basalt and anorthsite (uncommon on earth). The moon’s surface is much older than the earth.
What were the first materials to condense?
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.
Describe the model of homogenous accretion
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.
