I. Hot spots Stationary hot spots on Earth where heat rises (not at plate boundaries)

1. Hot spots and plate tectonics I. Hot spots Stationary hot spots on Earth where heat rises (not at plate boundaries) Hot spots produce volcanoes in plate interiors. Remain fixed relative to moving plates.

2. Hot spots, Geologic Time & Rock Cycle I. Hot spots B. Heat rising at hot spots melt rock in the crust—it rises and erupts. As the lithosphere moves over the hot spot it takes the newly formed volcanic edifice with it. 1. Seamounts - underwater volcanoes on sea floor 2. Volcanoes - have reached the water’s surface 3. guyots (ghee-owes) - not active any more, have eroded down below sea level

3. Hot spots, Geologic Time & Rock Cycle • I. Hot spots • C. As the plate moves, the hot spot forms a chain of volcanoes—records plate motion • Hawaii 6000km long (4000 miles) a. Kaua’i is the oldest Hawaiian island—5.1 million years old b. Hawaii is the youngest—still over the hot spot c. Loihi is a seamount, will be the next Hawaiian island (currently is ~9,000 feet tall from the seafloor, and still has several thousand meters to go before it reaches sea level—a few hundred thousand years

4. Hot spots, Geologic Time & Rock Cycle

5. Hot spots, Geologic Time & Rock Cycle I. Hot spots C. As the plate moves, the hot spot forms a chain of volcanoes—records plate motion As the moving plate carry each island away from the hot spot, the volcanoes loss their heat source and become extinct. Weathering and erosion gradually reduce the heights of the volvanoes above sea level.

6. II. Geologic Time • Earth is ~4.6 billion years old • Earth timeline across the US, each kilometer is ~1million years Time line across USA, 1 km = 1 Myr

7. Hot spots, Geologic Time & Rock Cycle 2. History of Earth all in a year: - Oldest rocks—mid-March - First life in the sea—May - Land plants and animals—November - Dinosaurs became dominant—Mid-December - Dinosaurs extinct—December 26th - Manlike creatures first started walking—evening of Dec 31st - Roman Empire—Dec 31st, 5 seconds: 11:59:45-11:59:50 - Columbus discovered America—3 seconds before midnight

8. Hot spots, Geologic Time & Rock Cycle B. Divisions of Geologic Time: based on fossils, so not equal amounts of time Earth history is divided into blocks of time during which important events occurred Based on fossils ages assigned to the divisions using isotopes in the later part of 20th century Time blocks are not equal lengths of time see page 290 in book

9. Geologic Time • 4 Eons—largest spans of time • Hadean (beneath Earth) oldest, 4.6 – 3.8 bya. Few rocks of this age left • Archean (ancient) 3.8 – 2.5 bya Earliest life on earth (bacteria 3.77 bya) (single-celled org 3.3 bya) • Proterozoic (early life) 2.5 bya – 545 mya. First multi-celled organisms • Phanerozoic (evident life) 545 mya – present

10. Geologic Time • 3 Erasin the Phanerozoic: • Divided based on dominant forms of life • Paleozoic: 545 – 245 mya age of invertebrates, fish, and amphibians • Mesozoic: 245 – 66.4 mya age of reptiles • Cenozoic: 66.4 – present age of mammals

11. Geologic Time 12 Periods in the Phanerozoic Less dramatic biological changes Cambrian Ordovician Silurian Devonian Mississippian Pennsylvanian Permian Triassic Jurassic Cretaceous Tertiary Quaternary

12. Rock Cycle III. Rock Cycle A. Definitions 1. Rock: naturally formed aggregate of one or more minerals 2. Mineral: naturally occurring inorganic solids with a definite chemical composition SiO2, CaCO3, Fe2SiO4, BaSO4, PbS 3. Rock Cycle—describes the processes by which the various rock types change over time

13. Rock Cycle The Rock Cycle 1. Magma—molten (liquid) rock that forms in certain places in the Earth’s interior where temperatures and pressures are such that rock melts - migrates up into crust 2. Crystallization - magma cools and solidifies a. It can erupt in a volcano and then it cools at the Earth’s surface - extrusive b. Or it crystallizes underground - intrusion 3. Igneous rocks - have cooled and solidified from molten material (lava or magma) either at or beneath the Earth’s surface

14. Rock Cycle 4. Weathering: any rock exposed at the Earth’s surface will undergo weathering - daily influences of the atmosphere slowly disintegrate & decompose rocks 5. Sediment: particles of rock and dissolved substances that have been removed from their original outcrop & transported. Sediments range in size from atoms dissolved off by acid rain to boulders Transported by erosional processes: running water, glaciers, wind, waves, etc. Deposited: usually in the ocean, but sometimes in river floodplains, desert basins, swamps, and sand dunes.

15. Rock Cycle 6. Lithification—“conversion (sediment) into rock” a. Compacted by weight of overlying sediment b. Cemented together when percolating water fills the pores with minerals 7. Sedimentary Rock: rock made up of sediment that has been lithified a. Can also form from the accumulated and compressed remains of certain plants and animals (shells in oceans & plants in swampscoal) b. Also from chemical precipitates of minerals previously dissolved in water (salt)

16. Rock Cycle • 8. Metamorphism • When rock is buried deep in the earth, it is subjected to intense heat and pressure • The rock changes mineralogy, chemical composition, and structure without melting (peanut butter and jelly sandwich example) • 9. Metamorphic rocks • 10. Melting: any rock if subjected to enough heat will melt (given that the pressure isn’t too high)

17. Rock Cycle • 8. Metamorphism • When rock is buried deep in the earth, it is subjected to intense heat and pressure • The rock changes mineralogy, chemical composition, and structure without melting (peanut butter and jelly sandwich example) • 9. Metamorphic rocks • 10. Melting: any rock if subjected to enough heat will melt (given that the pressure isn’t too high)

18. Rock Cycle • C. Alternative routes: • igneous rock  metamorphic rock • b. metamorphic rock  sediment • c. sedimentary rock  sediment