EARTH’S COMPONENTS & CHARACTERISTICS

1. EARTH’S COMPONENTS & CHARACTERISTICS UNIT 9 Environmental Geology APES

2. GEOLOGIC TIME SCALE • Organizes Earth’s 4.6 billion years of history into subgroups • Subgroups: • Eons • Eras • Periods • Epochs • 4 Major Eons…

3. 1. Hadean Eon • Oldest amount of time • 4.6-3.8 billion years ago • No rocks from this eon found on Earth • Evidence from meteorites & moon rocks

4. 2. Archean Eon • 3.8-2.5 billion years ago • 3.8 BYA Oldest rocks on Earth • 3.5 BYA oldest fossils of cells (prokaryotes) • 2.7 BYA atmospheric O2 begins to rise

5. 3. Proterozoic Eon • 2.5 billion – 543 million years ago. • 2.2 BYA oldest fossils eukaryotic cells • 600 MYA diverse algae & soft • Bodied invertes

6. 4. Phanerozoic Eon • 543 million years- present • Paleozoic Era • 543-248 million years • Diverse land plants, amphibians, reptiles, insects (Cambrian Explosion) • Mass extinction due to glaciation (global cooling)- killed 90% of species (end of Permian period) • Mesozoic Era • 248-66 million years • Age of Reptiles • Mass extinction due to climate change- 10-15% extinct (Cretaceous extinctions) • Cenozoic Era • 65 million years to present • Age of Mammals

7. STRUCTURE OF THE EARTH • Planetary differentiation- as more dense materials sank to center of earth, less dense material rose to surface

8. Layers of Earth • Core- center, mostly iron • Inner core- 1220 km thick, T & P cause iron to solidify • Outer core- 3480 km thick, liquid iron, creates magnetic field • Mantle- 70% of earth’s interior, made of O, Si, Mg • Asthenospere- closest to core, gelatinous, where magma is formed • Upper mantle- cooler, more solid, brittle • Crust- outermost layer • Crust + upper mantle make up lithosphere

9. Plate Tectonics • Tectonic plates- made of… • Uppermost mantle • Crust- 2 types: • Oceanic- thin (5-10 km), dense, rich in Fe, Mg, Si, below sea level • Continental- thick (20-70 km), less dense, rich in Ca, Na, K, Al • Constantly moving about 1-10 cm/year • 15 major plates- We are on North American Plate

10. Plate Boundaries • Where 2 plates meet • 3 types of plate boundaries

11. 1. Transform Boundaries • Plates slide past each other at transform faults • Movement is horizontal (strike-slip fault) • To the left- sinistral • To the right- dextral • Mostly smooth movement • If stuck, pressure builds, causes earthquakes

12. 2. Convergent Boundaries • 2 plates move toward each other • 3 types:

13. a. OCEANIC - CONTINENTAL • Oceanic plate is forced under continental plate • Called subduction • Creates deep-sea trench • Creates volcanic mountains along continental plate. • EX: Peru-Chile Trench and Andes Mountains of South America

14. b. OCEANIC - OCEANIC • Oceanic plate is forced under another oceanic plate • Called subduction • Crust melts into mantle • Creates deep-sea trench • Creates arc of volcanic islands that parallel trench • EX: Mariana Trench & Mariana Islands Aleutian Trench & Aleutian Islands

15. c.CONTINENTAL - CONTINENTAL • Two continental plates collide • Mountain ranges are created • EX: Himalayas- Indian plate forced under Eurasian plate

16. 3. Divergent Boundaries • 2 plates move apart • Creates rifts • Magma comes to surface & cools, creating crust • Usually in oceans, but can occur in continents (Africa’s Rift Valley) • Creates mid-ocean ridges • EX: Mid-Atlantic Ridge created when N.American plate pulls away from Eurasian plate.

17. CAUSES OF PLATE MOVEMENT • Convection currents • Hot mantle rises • Cools down • Cooled-down mantle sinks • Creates currents that move plates.

18. THEORY OF CONTINENTAL DRIFT • Alfred Wegner was first to propose theory of continental drift • He said: • All continents joined in large land mass called Pangea (Greek for “all land”) • Pangea began breaking up 200 million years ago. • Continents ended up where they are now • Continents are still moving

19. Evidence of Continental Drift • Fossils- similar plants & animals on widely separated continents • Rock Formations- similar rock types & stratification between 2 continents • Climate- Antarctica has coal deposits, indicating it had swamps, thus warmer weather= closer to equator

20. Geologic Hazards associated with Continental Drift • Earthquakes • Volcanoes • Landslides • Floods

21. Earthquakes • Epicenter- point where first movement occurs • Damage depends on soil underneath • Modern contractors build weak spots, pads/floats to absorb vibration • Underwater earthquakes cause tsunamis • Destroy coastal ecosystems • Saltwater infiltrates soil • sewage/industrial waste infect freshwater supplies

22. Volcanoes • Good • Created land (fertile soil), atmosphere, oceans • Bad • Release sulfur, combines with H20 to form sulfuric acid; interferes with solar radiation, cools climate (Mt. Pinatubo- Philippines) • Dust/Ash- can change climate by blocking sunlight (1815- Mt. Tambora in Indonesia, snowed in July in parts of New England, “year without a summer”) • Clouds of hot, toxic gases • Mudslides

23. Landslides • Mass wasting/movement • Usually slow & subtle, can happen all at once • Construction, forest clearing, agriculture, building on steep slopes increase frequency & damage

24. Flooding • Excess water that overflows stream banks • Contaminates everything- very costly • Pavement/buildings- speeds rate of runoff, soil has no chance to absorb • Floodplains- fertile, attract people/agriculture, affected most by flooding • READ chapter 16 on Natural Disasters!!