Unit 4 - Water. Earth s Interior. Earth s Interior. Continental Drift. Continental Drift. Continental Drift. Crust. Mantle. Core.

Transcription

1 Unit 4 - Water How did the oceans form? What special adaptations do saltwater organisms have? Where does our water come from? How do humans affect the Earth s water? Crust Rigid outer shell of Earth Oceanic and Continental Crust Mantle Upper mantle is partially molten Lower mantle is rigid (solid) Earth s Interior Earth s Interior Continental Drift Core Outer core is molten iron, source of Earth s magnetic field Inner core is solid, Iron and Nickel Continental Drift Earth s continents were joined as a single landmass Known as Pangaea Broke apart about 200 million years ago Continents slowly moved to their present locations Alfred Wegener Continental Drift Continental Drift Fossil evidence Fossils have been found for same species in areas with different climates Animals and plants did not swim across oceans Ex: lystrosaurus in central Africa and Antarctica Continental Drift Continental Drift Rock evidence Identical rock formations found on different continents Ex: Appalachians in US and Scottish Highlands 1

2 Continental Drift Continental Drift Climate evidence Coal deposits in Antarctica Glaciers found in warm climate regions Plate Tectonics Tectonic Plates Large plates of earth s crust Some contain ocean and land Fit together at edges Move ~2-15 cm/year Due to convection currents Plate Boundaries Divergent Boundary Two tectonic plates move apart from each other Causes: Mid-Ocean Ridges Rift valleys Long, narrow depressions Plate Boundaries Convergent Boundary Two tectonic plates move towards each other (come together) Subduction Process when one tectonic plate slips beneath another plate Oceanic Plates are more dense than continental Convergent Plate Boundaries Oceanic Oceanic Subduction Occurs Causes deep sea trenches Ex: Marianas Trench (11 km deep) Convergent Plate Boundaries Oceanic Continental Subduction Occurs Trench and Volcanic Arch (Peru Chile Trench) 2

3 Convergent Plate Boundaries Continental Continental No Subduction Occurs Causes mountain building Ex: Himalayas Plate Boundaries Transform Boundary Two plates slide past each other Often causes Earthquakes Ex: San Andreas Fault Seafloor Spreading Seafloor Spreading New ocean crust is formed at mid-ocean ridges and destroyed at deep sea trenches Occurs in a continuous cycle Seafloor Spreading Mid-Ocean Ridges Underwater Mountain Chain Divergent Plate boundaries Create New Seafloor Spreading Deep-Sea Trenches Narrow Elongated depression in seafloor Very steep sides Convergent Plate boundaries Seafloor Spreading Seafloor Spreading Process 1. Magma (hotter and less dense than crust) forced up and fills gap in ridge 2. Magma solidifies, becoming new ocean floor 3. More magma is forced upward and the crust moves away from ridge 4. Crust is destroyed by subduction at trenches 3

4 Continental Margin Area where the edges of the continents meet the ocean Shallowest part of ocean Includes continental shelf, slope, and rise Continental Shelf Shallowest part of continental margin Extends into ocean from shore Average width 60 km, Depth 130 m Home to small fish and coral Continental Slope Quick drop in the seafloor True edge of continent Turbidity Currents Fast moving water currents along sea floor that carve out submarine canyons Continental Rise Accumulation of sediment at bottom of continental slope Less sloped Many unique life forms Abyssal Plains Flattest part of the ocean floor 5 to 6 km below surface No sunlight Little life exists Seamounts Underwater basaltic volcanoes Diversity of life forms Usually extinct volcanoes Guyots Large, extinct, volcanoes with flat submerged tops 4

5 Volcanic Islands Formed from seamounts that breach the surface Often near convergent boundaries Ex: Hawaii The Ocean Ocean One continuous body of saltwater Split into 5 basins Pacific, Atlantic, Indian, Arctic, and Southern Seas are partially surrounded by land The Ocean Ocean 71 % of Earth s Surface 97.5 % of water on Earth Avg. surface temp 63 F More than 200,000 species Likely > 1,000,000 The Ocean Ocean Formation Comets Ice melted and filled in basins Volcanoes Water vapor is often released in eruption Measure of dissolved salts in water Varies with temperature and depth 3.5% Dissolved salts NaCl is most abundant 5

6 Average ocean salinity is 35 ppt Freshwater < 0.5 ppt Brackish Water ppt Where rivers meet sea/ocean Ex: Barnegat Bay Caused by: Runoff Water carrying sediment and dissolved salts Weathering/Erosion of rocks/minerals Sediment dissolves in water Caused by: Hydrothermal vents Cracks that release gases to water Near divergent boundaries or volcanoes Increased by: Evaporation Ocean freezing Decreased by: Rainfall Runoff from rivers Melting of ice Intertidal Zone Between lowest and highest tide Underwater at high, exposed at low High biodiversity Ex: crab, mussel Neritic Zone Between low tide and continental edge Generally receives light Shelter and food for animals Protect shoreline erosion Ex: Kelp Forest 6

7 Open-Ocean Zone 90 % of ocean Mostly dark and unproductive Many scavengers due to limited food Photic Zone Light reaches through Near the surface of the water ~ 200 m depth in ocean Most productive zone Aphotic Zone No light reaches through No photosynthesis occurs Very cold near bottom (~2 4 C) High Pressure (>100 atm) Water moves very slowly Benthic Zone Floor of the ocean Wide variety of life due to depth differences across Earth Adapted to high pressure at sea floor Coral Reef Coral Invertebrates related to jellyfish and anemones Often found in groups of polyps Coral Reef Coral Reef Mass of calcium carbonate with skeletons of coral Old skeletons are part of the reef while new polyps grow Found near tropics 7

8 Coral Reef Coral Reef Like rainforest of the sea High biodiversity Nutrient poor surroundings Often very colorful Coral Reef Coral Reef Benefits Protect shoreline from wave energy High biodiversity Commercial fishing sites Ecotourism Chemicals for medical research Coral Reef Coral Reef Threats Pollution Overfishing ph changes Bleaching Algae blooms About 60 % of reefs are at risk 8