Origin of Earth, Atmosphere, and Ocean: Planetary Geology Overview

1. Origin of earth, its atmosphere and Ocean …

2. The Milky Way Galaxy Where are we? Fig. 2-1

3. Origin of the Solar System and Earth Fig. 2-5. The nebular hypothesis. Contraction of gas and dust to form protosun and early planets. The protoplanets were mostly homogenous.

4. Basalt (ocean) Granite (continent) Fe Mg Si Fe Ni Fig. 2-6. Earth’s layered structure, result of density stratification in early Earth when radioactivity kept Earth hot and molten.

5. Sun Jupiter Saturn Neptune Uranus Mercury Earth Mars Pluto terrestrial planets (mostly rock & metallic) Gas Giant planets (H, He) w/ rock/ice satellites Planetary Geology Overview of Planets The planets’ composition changes with distance to the Sun Venus

6. Impact origin of the Moon!

7. ‘Deep Time’ Figure 2B. Major events in the evolution of Earth pictured as a cone. TSP

8. See 2-15

9. Geologic time scale - a calendar of Earth’s history eons Phanerozoic - last 570 million years Cenozoic - recent life Mesozoic - age of middle life Paleozoic - ancient life Precambrian - from birth of Earth up to before complex life forms developed eras 0-66.4 m.y.a (mammals, humans) Massive extinction events 66.4-245 m.y.a (dinosaurs, 1st scrawny mammals) 245-540 m.y.a (first fossils with shells, fish, trilobites, clams, corals, ferns ) (algae, bacteria, some fossils without shells like jellyfish, worms)

10. How do we determine geologic age? Half of the uranium has decayed Fig. 2-14 One fourth of the uranium has decayed ‘Radiometric age dating’: Radioactive decay of natural elements can be used as a clock, by determining the ratio of the radioactive element with its decay product. ‘Half-life’ is the time it takes for half of the atoms of the radioactive element to decay to atoms of the other element.

11. Origin of atmosphere and ocean Fig. 2-7 I. Outgassing Widespread volcanic activity released water vapor and smaller quantities of CO2, chlorine gas and hydrogen. As earth cooled, water vapour condensed (1) and fell to the earth’s surface (2) where it accumulated to form the oceans (3). Early atmosphere consists mainly of H2O, H2, He, CO2, NH4, CH4 H2O II. Comets An additional source of water on Earth (back then and now) are icy comets. (arrive at about 5-30 /min, Are in average 2 m (40 feet) in diameter.

12. A brief introduction to minerals, rocks and the rock cycle

13. Minerals: thebuilding Minerals blocks of rocks Definition of a mineral -> To be considered a mineral, it must: 1. Occur naturally 2. Be inorganic 3. Be a solid 4. Possess an orderly internal structure 5. Have a definite chemical composition

14. Minerals: thebuilding Minerals blocks of rocks Definition of a rock -> different from that of a mineral. A rock: 1) is solid 2) contains a mixture of one or more minerals 3) May contain a non-mineral 4) occurs naturally as part of our planet

15. Minerals: thebuilding Minerals blocks of rocks Rocks and minerals • Some rocks composed entirely of one mineral • limestone (calcite) • Most rocks have more than one kind of mineral • granite • Some rocks contain non-mineral matter • coal (has organic debris) • obsidian (volcanic glassy rock -> not crystalline)

16. The composition of minerals Minerals • Atomic structure Granite & constituent minerals

17. The composition of minerals Minerals • Breaking Things Down: Atomic structure So far we have: minerals rock mineral collection of one or more minerals A collection of one or more types of atoms

18. The composition of minerals Minerals • Atomic structure • atom: smallest piece of matter with unique chemical properties -> extremely small • element: a substance consisting of identical atoms

19. Atomic structure The composition of minerals Minerals Periodic table of the elements

20. The composition of minerals Minerals • Atomic structure 112 known elements Only 92 occur naturally

21. Minerals • Over 4000 minerals: only few dozen are abundant, making up most rocks of Earth’s crust • => rock-forming minerals • Only 8 elements make up most of crust’s minerals & represent over 98% of the continental crust • The two most abundant elements: • Silicon (Si) • Oxygen (O)

22. Minerals Percent of elements by WEIGHT Average composition of the continental crust

23. Mineral groups • The silicates Silicon and Oxygen combine to form the most common mineral group, the silicates. Every silicate mineral contains the elements silicon (Si) oxygen (O) Nearly every silicate mineral combines with one or more additional elements to achieve electrical neutrality

24. 1) Mineral groups • The silicates The fundamental building block of all silicates is the silicon-oxygen tetrahedron Two different views of this arrangement: silicon atom oxygen atoms

25. 1) Mineral groups The silicates Remember: Silicates are the most abundant mineral group with the silicate ion as basic building block. Light colored (crust, esp. continental crust) Non-ferromagnesian (felsic) silicates Feldspar (Si, O, Al, K, Na, Ca) - mostly white or pink 50% of earth’s crust ! Quartz (SiO2=silica) - commonly transparent silicate that consists only of silicon and oxygen second most abundant in crust! Muscovite (Si, O, Al, K, H) – most common mica cleavage in sheets, glass in Middle ages sparkle in rocks, mica flakes in sand Dark colored (mantle and oceanic crust) Olivine (Si, O, Fe, Mg, Ca)

26. Mineral groups The silicates Remember: Silicates are the most abundant mineral group with the silicate ion as basic building block. Dark colored (mantle, basalt, continental crust) Ferromagnesian (mafic) are dark silicates, contain ions of iron and/or magnesium) Olivine – black to olive green, in basalt Pyroxene – important component of earth’s mantle Hornblende – important component of continental rock Biotite – iron rich mica, component of continental rock Dark colored (mantle and oceanic crust) Olivine (Si, O, Fe, Mg, Ca)

27. Mineral groups • Important Nonsilicate Minerals Carbonates (CO3 2-) = carbonate ion Calcite (CaCO3) Dolomite (CaMg(CO3)2 Forms limestone Calcium/magnesium Carbonate, forms dolostone  found together in sedimentary rock limestone,  Main ingredient to cement, roads & building stones

28. Mineral groups • Important Nonsilicate Minerals Halides Halite (NaCl) -> common table salt Sulfates Gypsum (CaSO4-H2O) -> calcium sulfate + water, main ingredient of plaster & other building materials Oxides Hematite (Fe2O3) -> mined for iron, steel Ice (H2O) -> solid form of water

29. Rocks Three major types of rock

30. Rocks Rock cycle

31. How to make a sedimentary rock. Sedimentary rocks Diagenesis Any physical and chemical change that happens to the sediments or the sedimentary rock Fig. 8.11

32. How to make a metamorphic rock. Transform: Igneous Sedimentary Metamorphic into: “process” Metamorphic occurs through pressure, temperature, and hydrothermal fluids Recall: 3 fundamental rock types “metamorphism” Lit. “change form”

33. Metamorphic rocks Metamorphic rocks form under 4 main conditions: Rocks

34. Chapter 4: Rocks Rock cycle