2FOCUS QUESTIONSWhat are the major physical features of the Earth’s surface?What explanation have scientists developed for the existence and distribution of these features?How do these features affect the Earth’s oceans?
3The Water Planet 71% of earth covered in ocean Oceans regulate climate and atmosphereFour large basins:Pacific – largest and deepestAtlanticIndianArctic – smallest and shallowest(Southern ocean – continuous body of water surrounding Antarctica)Large basins connected by smaller, shallow seas
4Our Fledgling Planet Earth – approximately 4.5 billion years old Formed from an aggregation of dust clouds and gas particles that condensed into solid matter.Intense heating melted many of these heavier elements in the core and mantle of the planet.The uppermost of layers cooled and formed the Earth’s crust.
5The Structure of the Earth Materials have settled in the planet according to their density.d = m/VLithosphere (crust – very thin)Asthenosphere (upper mantle – fluid)Mesosphere (mid to lower mantle – solid but very hot)Core (mixtures of iron – inner is solid, outer is molten)
6All Crust is not the Same Continental crust is composed of granite.Oceanic crust is composed of basalt.Continental crust is:lighterthicker (20-50 km vs. 5 km for ocean)less densegeologically older… than Oceanic crust.See Table 2.2 on page 24
7Hypothesis of Continental Drift Developed by Alfred Wegener in 1915.Proposed that present continents had drifted apart after the breakup of a single supercontinent, Pangaea.Hypothesis not widely accepted (How?)
9Theory of Plate Tectonics Plate tectonics – the study of the processes by which the lithosphere moves laterally across the asthenosphere.This hypothesis is supported by:presence of the mid-ocean ridgecomparative fossil data from different continentsapparent puzzle-piece shape of different continentsmagnetic reversal and sediment patterns on the sea floordistribution of geological features on the Earth
10Plate Tectonics in Action Plates “float” on the asthenosphere.There are areas where plates spread apart……and areas where plates collide.Mid-ocean Ridges/ RiftsSubduction zones/ Trenches
12Types of Boundaries Convergence – plates collide Oceanic-continental convergenceContinental-continental convergenceOceanic-oceanic convergenceShear Boundary – plates slide past each otherDivergence – plates separateMid-ocean ridgeTransforms faultsRift valleys
13Oceanic-Continental Boundaries Heavy oceanic crust slides under continent.Called subduction.Trench forms.Causes explosive earthquakes.Molten lithosphere seeps up through continental crust and forms volcanoes.
14Oceanic-Oceanic Boundaries One plate will slide under the other.Trench forms.Slow-flowing volcanoes formsometimes break the ocean surface (island arcs).Examples:Aleutian Islands, AKMariana Islands
15Continental-Continental Boundaries Two continents smash against one another with force and become “welded” together.Crust buckles forming mountain ranges.No trenches or volcanoes.India Collision (Animation)(http://geology-guy.com/teaching/iac/animations/india_asia_collision.htm)
16Californians Get Closer Together In addition the Pacific Plate (which contains the city of Los Angeles) and the North American Plate (which contains San Francisco) share a shear boundary.These two plates slide past each other such that these cities get 4 inches closer each year.In addition the Pacific Plate (which contains the city of Los Angeles) and the North American Plate (which contains San Francisco) are actually sliding such that these cities get 4 inches closer to one another each year.These cities are roughly 380 miles apart. So they will be one city in 6,019,200 years.
17The Mid-Ocean Ridge and Transform Faults A continuous chain of submarine volcanic mountains that circles the globeCaused by rising of hot mantle and pushes apart oceanic platesResults in sea floor spreading
18The Mid-Ocean Ridge and Transform Faults Displaced at regular intervals by transform faults.Occasionally breaks the surface at places like Iceland and the Azores.Examples:Mid-Atlantic RidgeEast Pacific RiseAbove: Mid-Atlantic Ridge Left: Iceland –showing ridge
19Rift ValleysA gap or depression resulting in the center of a mid-ocean ridge or on land.African Rift Valley
20Features of Mid-Ocean Rifts Hydrothermal vents – deep water hot-springs that dissolve minerals in the Earth’s crust (mainly sulfides)(http://oceanexplorer.noaa.gov/edu/learning/player/lesson05.html)Black smokers – chimney-like structures that build up deposits of minerals and “smoke” a cloud of mineral particles.Hot Spots – sporadic areas where molten magma forces its way through the lithosphere; creates volcanic activity (Hawaiian Islands)(http://www.youtube.com/watch?v=hOCfb9ox_90&feature=related)
21Geological “Hot Spots” Occur in over 100 places on the globeAreas where hot magma sporadically forces its way through the lithosphere to erupt in volcanic activity.Examples:Hawaiian IslandsYellowstone National Park
22Hot Spot FormationAlthough this model has been contested, it describes a stationary magma source over which plates slide.
27Geological Provinces of the Ocean Floor Based on previous knowledge and logic, label the following parts of the map:Abyssal plainContinental riseContinental shelfContinental slopeGuyotSeamountShelf breakTrench
30Geological Provinces of the Ocean Floor A. Continental shelf – The shallow gently sloping section of the continental margin that extends from the shore to the point where the slope gets steeper.B. Shelf break – The section of the continental shelf where the slope abruptly becomes steeper, usually at a depth of 120 to 200 m (400 to 600 ft).C. Continental Slope – The steeper, seaward section of the continental margin.D. Continental Rise –The gently sloping area at the base of the continental slope.Abyssal Plain – The nearly flat region of the deep-sea floor.Guyot – A flat topped- seamountTrench – A narrow deep depression in the sea floor.Seamount – A submarine volcano in the abyssal plain
31Global Seafloor Topography Global Seafloor Topogrpahy taken from the websiteGlobal Seafloor Topography
32Continental MarginsActive Margin – a continental margin that is colliding with another plate and as a result is geologically activePassive Margin – a continental margin that is located at the trailing edge of a continent and as a result shows little geological activity
35Comparative Fossil/Sediment Data Geologists noted the similarities between the fossils and sediment deposits found on opposite sides of the Atlantic Ocean.
36Magnetic ReversalsRocks contain magnetic particles that align with the Earth’s magnetic field.During periods called magnetic reversals, the Earth’s north pole switches to the opposite side of the globe as it is now.Believed to be related to movements in the Earth’s molten core.
37Magnetic AnomaliesWhen molten rock comes to the surface, the magnetic particles are free to align with the Earth’s magnetic pole.When the rock cools, the particles are fixed in the magnetic orientation at the time.
38Magnetic AnomaliesGeologists have thus discovered a pattern of magnetic banding parallel to the mid-ocean ridge.
48Results of an O2 Rich Atmosphere Aerobic organisms began to out-compete anaerobes.Excess oxygen begins to react in the high atmosphere with ultraviolet radiation. This creates ozone (O3)prevents harmful UV rays from penetrating to the earth.Allows organisms to colonize the land.Also, Earth ideally settled in an orbit where molecular water can exist in all three statesparticularly the liquid state!
49SedimentsLithogenous sediment – results from the physical and chemical weathering of rocks on land.Carried by run-off and rivers to the ocean.Biogenous sediment – skeletons and shells of marine organisms that have fallen to the ocean floor.Diatoms, radiolarians, foraminiferans, and coccolithophorids
50Biogenous sedimentsCalcareous ooze – skeletons composed of calcium carbonate (CaCO3)Siliceous ooze – skeletons composed of silica (SiO2).
51Sea Level ChangeInterglacials – warm periods during which freshwater melts and sea level rises.Ice ages – cold periods when large amounts of water are stored in ice caps and glaciers and sea level drops.
52Greenhouse EffectGlobal temperatures and the rate of glacial melting are rapidly increasing.Still uncertainty as to whether this is a natural phenomenon or whether it has been accelerated by humans.