Elements in cosmic origin of earth theory
- 1. Origin of Earth • Age of universe is ~ 14.5 By, about 10 By older than Earth • Early universe had only protons & helium nuclei as condensed particles, rest was elementary particles & radiation • First stars formed from hydrogen and helium, rest of elements formed in protostars by nucleosynthesis • Stars exploded as supernovae, scattering hydrogen, He & newly formed elements as intergalactic “dust”. Other stars became “black holes”, brown dwarfs, etc. • Inhomogeneities in dust clouds led to formation of secondary stars, similar to our sun, contain orbiting debris formed from elements in 1st generation stars. • Inherited angular momentum caused debris to orbit main condensation center, and eventually gave rise to orbiting planets
- 2. “Hadean” 4.6 by age , Earth formed by accretion and meteorite bombardment. It was truly “hell on earth” as constant meteorite bombardment and high interior heat flow combined to keep early Earth surface in nearly constant molten state. Atmosphere of early Earth likely reducing (i.e. no oxygen), mostly: methane (CH4), ammonia (NH3), hydrogen (H2) and helium (He) with some traces of noble gases like neon (Ne)
- 3. Stages in Planetary Evolution Planetesimals … small bodies formed from dust and gas eddies Planets formed from planetesimals by gravitational attraction.
- 4. (A) homogeneous, low-density protoplanet to (B) a dense, differentiated planet
- 5. Eearth’s interior 1. Crust (solid) 2. Mantle (solid) 3. Outer core (liquid) 4. Inner core (solid) Discontinuity at core- mantle boundary
- 7. Earth's interior Upper mantle Subduction zones Midocean ridges Region where basaltic magma forms
- 9. Moho (M) boundary between crust and upper mantle, based on seismic analysis from earthquakes.
- 10. Differentiation of Chemical Elements in Earth
- 11. Density stratification with regard to gases (lightest farthest out, heaviest closer to Earth surface). (vertical scale is logarithmic). Atmospheric Stratification and types of Radiation
- 12. Evolution of Earth’s atmosphere from early Hadean (5 Bya) to present. Important change from Stage II to Stage III was rise in oxygen (due to evolution of photosynthetic algae). Noble gases, Ar, Ne, He and Kr, from degassing upper mantle which continues to today.