Formation of Earth Birth of the Solar System

Formation of Earth Birth of the Solar System Nebular Theory – Nebula compresses – Rotation flattens nebula – Collapse into center formed solar nebula and finally, the sun – Condensation formed planets, planetesimal, moons and asteroids during planetary accretion around 4. 6 billion years ago – (Meteorites are iron-rich or rocky fragments left over from planetary accretion) See Fig. 1. 9 (a), (b) and (c) http: //www. psi. edu/projects/planets. html

Orion Nebula www. hubblesite. org www. geol. umd. edu/~kaufman/ ppt/chapter 4/sld 002. htm www. psi. edu/projects/ planets/planets. html See Fig. 1. 9

Formation of the Planets • Nuclear fusion began Terrestrial Planets within the mass at the center of the solar system forming the sun • The inner planets were hotter and gas was driven away leaving the terrestrial (rocky) planets • The outer planets were cooler and more massive ? so they collected and Gas Giants retained the gasses hence the “Gas Giants” www. amnh. org/rose/backgrounds. html

Differentiation of the Planets • The relatively uniform iron-rich proto planets began to separate into zones of different composition: 4. 5 bya • Heat from meteor impact, pressure and radioactive elements cause iron (and nickel) to melt and sink to the center of the terrestrial planets See Fig 1. 10

Further Differentiation of Earth • Lighter elements such as Oxygen, Silicon, and Mid-Ocean Aluminum rose to form a (New. Ridge Crust) thin, rigid crust • The crust, which was originally thin and basaltic (iron rich silicate), further differentiated to form continental crust which is thicker, iron poor, silica rich and lighter Deepest Mine Deepest Well Continental Crust (Silicic) Oceanic Crust (Basalt) See Fig. 1. 11

Composition of Earth and Crust Element (Atomic #) Chemical Symbol Before and After Differentiation % of Change in whole Crust Due to Earth (by Weight) Differentiation Oxygen (8) O 30 46. 6 Increase Silicon (14) Si 15 27. 7 Increase Aluminum (13) Al <1 8. 1 Increase Iron (26) Fe 35 5. 0 Decrease Calcium (20) Ca <1 3. 6 Increase Sodium (11) Na <1 2. 8 Increase Potassium (19) K <1 2. 6 Increase Magnesium (12) Mg 10 2. 1 Decrease ~8 1. 5 All Others

Crust and Mantle Lithosphere and Asthenosphere • The uppermost mantle and crust are rigid solid rock (Lithosphere) • The rest of the mantle is soft but solid (Asthenosphere) • The Continental Crust “floats” on the uppermost mantle • The denser, thinner Oceanic Crust comprises the ocean Figure 1. 11, Detail of crust and Mantle basins

A Large Variety of Rocks (and Sediment) Products of an Active Planet Earth’s structure leads to intense geologic activity – Inner core: Solid iron – Outer core: Liquid iron, convecting (magnetic field) – Mantle (Asthenosphere) : plastic solid, iron-magnesium silicate, convecting – Crust (Lithosphere): Rigid, thin • O, Si, Al, Fe, Ca, Na, K, Mg… 47%, 28, 8, 5, 4, 3, 2 Crust: Rigid, Thin Mantle: Plastic, Convecting

Lithospheric Plates See Kehew, Figure 1. 19 • The Lithosphere is broken into “plates” (7 maj. , 6 or 7 min. ) • Plates that “ride around” on the flowing Asthenosphere • Carrying the continents and causing continental drift

Lithospheric Plates Fig. 1. 13 and 2. 14

Three Types of Plate Boundaries • Divergent • Convergent • Transform See Fig. 1. 14 and 1. 13

Things to Know About Plate Tectonics • Composition and properties of Zones – Iron core (solid & liquid, convecting, magnetic field) – Mantle: Plastic solid, convecting, ultramafic (Si, O, Fe, Mg) • Composition and Properties of the Crust – Oceanic Crust: Basalt, Thin (5 -10 km) (O, Si, Fe, Mg, Ca) – Continental Crust: Granitic, Thick (10 -50 km) (O, Si, Al, Na, K)

Things to Know About Plate Tectonics • Features and Geologic Phenomena – Convergent: trenches, mountain chains, granitic magma, granitic rocks, composite volcanoes, – Divergent: Mid ocean ridges, rift valleys, shallow earthquakes, basaltic magma and lava, basalt, lava floods (volcanoes rare)

Things to Know About Plate Tectonics • Features and Geologic Phenomena – Transform: Offset ocean ridges or mountain chains, shallow earthquakes, no magma or lava – Hotspots: Shallow earthquakes, basaltic magma and lava, basalt, lava floods, sometimes shield volcanoes

Rock entar y Sedim • Igneous Rocks: When rocks melt, Magma is formed, rises, cools and crystallizes. • Sedimentary Rocks: All rocks weather and erode to form sediments (e. g. , gravel, sand, silt, and clay). When these sediments accumulate they are compressed and cemented (lithified) • Metamorphic Rocks: When rocks are compressed and heated but not melted their minerals re-equilibrate (metamorphose) to minerals stable at higher temperatures and pressures s The 3 rock types form at convergent plate boundaries Metam orphi Rocks c Igneous Rocks Magma

The Rock Cycle Geological Materials Transformation Processes • Geologic materials (blocks) • Are transformed and transported • By geologic processes (arrows) • To form other geologic materials • Driven by internal and external processes Fig. 3. 1 See Fig. 1. 15

Igneous and Sedimentary Rocks at Divergent Boundaries and Passive Margins • Igneous Rocks (basalt) are formed at divergent plate boundaries and Mantle Hot Spots. New basaltic, oceanic crust is generated at divergent plate boundaries. • Sedimentary Rocks are formed along active and passive continental margins from sediments shed from continents • Sedimentary Rocks are formed on continents where a basin forms and sediments accumulate to great thicknesses. E. g. , adjacent to mountain ranges and within rift valleys.

Learning Plate Tectonic Geography Brushing up on basic geography will help you learn Plate Tectonics Once you know your basic geography and ocean basin features (Mid Ocean Ridges, -Oceanic Trenches) you can - Learn the 7 major plates - Learn the types of plate boundaries - Learn why those features are where they are