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6.2: Cosmogenous Sediments

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    9973
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    Cosmogenous Sediments

    Cosmogenous sediments originated from outer space. Scientists have used satellites to estimate how much material enters the earth's atmosphere. Current estimates from satellite data suggesting about 100 to 300 tons (mostly cosmic dust) hits earth each day. This is just a tiny fraction of the sediments generated on earth each day. However, early in the history of our Solar System, Earth and other planets, moons, comets and asteroids formed from the gravitational accumulation of extraterrestrial material, but by 4.5 million years ago, most of this cosmogenous accumulation had significantly diminished. However, cosmogenous materials including iron-nickel and stony meteorites can be found. Although a relatively insignificant source of sediment, meteor fireballs disintegrating in the atmosphere contribute dust that can accumulate measurable amounts in parts of some ocean basins.

    Extraterrestrial impacts have changed life on Earth repeatedly, including the mass extinction at the end of the Mesozoic Era associated with the extinction of dinosaurs and many other forms of life on land and in the oceans. Tektites are silica glass generated by extraterrestrial impacts: asteroids exploding on the surface and molten material is ejected into the atmosphere where it condenses into a glass-like material.

    bollide meteorite tectite
    Figure 6.2. A meteor fireball (a bolide) disintegrates in the night sky over Oklahoma. Figure 6.3. Iron-nickel meteorite from the Diablo Canyon area, AZ (see below) Figure 6.4. A tektite is a ball of glass-like material ejected by an asteroid impact.
    bollide events Meteor Crater near flagstaff Arizona Cretaceous-Tertiary boundary
    Figure 6.5. Known locations of bolide events (1994 to 2013). Bolides are meteor fireballs that explode when entering the atmosphere. Few reach the ground or oceans. Figure 6.6. Meteor Crater (Diablo Canyon site) near Flagstaff Arizona is a 50,000 year-old asteroid impact site about a mile in diameter and 550 feet deep. Figure 6.7. The Cretaceous-Tertiary extinction event is preserved in sediments in many locations around the world. This one is in South Dakota.
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