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 O 2 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 H 2 0 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!!