Test Thursday October 23 Know and understand these reactions: Photosynthesis CO2 + H2O CH2O + O2 Respiration CH2O + O2 CO2 + H2O Calcite Dissolution and Precipitation 2+ CaCO3 + CO2 + H2O Ca + 2HCO3 Be able to derive the equation for radioactive decay Chapters 4, 5, 6, 11, 12, 13 Format similar to Exam 1 Paleozoic era: Life explodes During the Paleozoic, organisms diversified dramatically A mass extinction at the close of the Paleozoic destroyed 70% of all vertebrate species on land and 90% of all marine organisms Figure 12.A (left) Figure 12.A (right) Mesozoic Era: Age of the dinosaurs Mesozoic, literally the era of middle life, is often called the Age of Reptiles Organisms that survived the extinction at the end of the Paleozoic began to diversify Gymnosperms (cycads, conifers, and ginkgoes) became the dominant trees of the Mesozoic Reptiles became the dominant land animals First reptiles were small, but evolved rapidly, particularly the dinosaurs Mesozoic Era: Age of the dinosaurs Mesozoic, literally the era of middle life, is often called the Age of Reptiles Organisms that survived the extinction at the end of the Paleozoic began to diversify Diversity of reptiles included large carnivorous dinosaurs, even larger herbivorous dinosaurs such as Apatosaurus, pterosaurs or flying reptiles, and Archaeopteryx, the predecessor of modern birds Archaeopteryx fossil Figure 12.32 Mesozoic Era: Age of the dinosaurs Mesozoic, literally the era of middle life, is often called the Age of Reptiles At the close of the Mesozoic, many reptile groups became extinct A few types survived, including the turtles, snakes, and lizards Cretaceous Tertiary Boundary Layer Cenozoic Era: Age of mammals In the Cenozoic, mammals replaced the reptiles as the dominant vertebrate life-forms on land Two groups evolved, the marsupials and the placentals One tendency was for some mammal groups to become very large Late Pleistocene extinctions eliminated these larger animals Cenozoic Era: Age of mammals The Cenozoic could also be called the Age of Flowering Plants Flowering plants (angiosperms) strongly influenced the evolution of both birds and herbivorous mammals throughout the Cenozoic Major reptile groups in the Mesozoic era Lecture 15 Ocean Floor The vast world ocean Earth is often referred to as the blue planet Seventy-one percent of Earth s surface is represented by oceans and marginal seas Continents and islands comprise the remaining 29% Northern Hemisphere is called the land hemisphere, and the Southern Hemisphere the water hemisphere Views of the Northern and Southern hemispheres The vast world ocean Four main <a href="/keyword/ocean-basins/" >ocean basins</a> Pacific Ocean - the largest and has the greatest depth Atlantic Ocean about half the size of the Pacific and not quite as deep Indian Ocean slightly smaller than the Atlantic, largely a southern Hemisphere body Arctic Ocean about 7 percent the size of the Pacific The oceans of Earth Where does this picture come from?? The Study of Ocean Floor Contours Bathymetry How did early scientists study the ocean floor? Advances in Bathymetry Echo sounding Multibeam Systems Satellite Altimetry Side Scan Sonar Echo Sounding accuracy affected by water conditions and bottom contours Speed of Sound in seawater = 1500 m/sec. However, Echo sounders will depend on? Temperature, Pressure, Salinity, Seafloor Density, AND The assumption that the ship is only receiving vertical pulses back Multibeam Systems ping every 10 sec mow the lawn to cover seafloor only 200 ships have multibeams it would take +125yrs to map seafloor Sidescan Sonar SONAR (Sound Navigation and Ranging) Similar to ecosounder Measures acoustic return intensity Does not measure depth. Measures bottom type (sand mud gravel) bottom features (cables, pipelines, sunken ships) Bedforms (ripples, sand dunes, ledges, submarine ridges) Sidescan sonar principle of operation Sound source Weak return intensity High return intensity Shadow zone shadow high intermediate weak 50 m Sidescan image from a sandy <a href="/keyword/continental-shelf/" >continental shelf</a> Vehicle track line Shadow zone Ripples Satellite Altimetry Geosat, US Navy satellite (1985 90) (Topex/Poseidon now) Measure sea height (3 cm) Underwater features create gravitational pull on seawater and induce variation in sea surface height Geoid Variation in Sea Surface Height - distortion of sea surface above seabed features is due to extra gravitational pull From Satellite Images Where is the Deepest Part of the Ocean Usually Found?? Most people think that the ocean bottom is like a bathtub with the deepest part in the middle of the ocean .not true Cross Sections of the Atlantic and Pacific <a href="/keyword/ocean-basins/" >ocean basins</a> (vertical scale exaggerated) Mapping the ocean floor Three major topographic units of the ocean floor Continental margins Ocean basin floor Mid-ocean ridge Major topographic divisions of the North Atlantic Ocean Continental margins Passive continental margins Found along most coastal area that surround the Atlantic Ocean Not associated with plate boundaries Experience little volcanism and Few earthquakes Features of a passive continental margin Continental margins Passive continental margins Features comprising a passive continental margin <a href="/keyword/continental-shelf/" >continental shelf</a> Flooded extension of the continent Varies greatly in width Gently sloping Contains oil and important mineral deposits Continental margins Passive continental margins Features comprising a passive continental margin <a href="/keyword/continental-shelf/" >continental shelf</a> Some areas are mantled by extensive glacial deposits Most consist of thick accumulations of shallowwater sediments Continental margins Passive continental margins Features comprising a passive continental margin Continental slope Marks the seaward edge of the <a href="/keyword/continental-shelf/" >continental shelf</a> Relatively steep structure Boundary between continental crust and oceanic crust Continental margins Passive continental margins Features comprising a passive continental margin Submarine canyons and turbidity currents Submarine canyons Deep, steep-sided valleys cut into the continental slope Some are seaward extensions of river valleys Most appear to have been eroded by turbidity currents Continental margins Passive continental margins Features comprising a passive continental margin Submarine canyons and turbidity currents Turbidity currents Downslope movements of dense, sedimentladen water Deposits are called turbidites Relict Sediment Turbidity currents Submarine Canyons Formed by erosion from turbidity currents Continental margins Passive continental margins Features comprising a passive continental margin Continental rise Found in regions where trenches are absent Continental slope merges into a more gradual incline the continental rise Thick accumulation of sediment At the base of the continental slope turbidity currents that follow submarine canyons deposit sediment that forms deep-sea fans Features of a passive continental margin <a href="/keyword/continental-shelf/" >continental shelf</a> Extends from shoreline to shelf break Wide gently sloping (1:1000) Shelf Break (~ 100 m isobath) Slope Extends from break to rise Relatively steep (1:40) (unstable) Sediment bypass, often exposed bedrock Rise Extends from slope to abyssal plain Intermediate (1:100 to 1:700) Oceanic crust Thick sediment deposits Continental margins Active continental margins Continental slope descends abruptly into a deep-ocean trench Located primarily around the Pacific Ocean Accumulations of deformed sediment and scraps of ocean crust form accretionary wedges Some subduction zones have little or no accumulation of sediments Ocean basin floor Deep-ocean trenches Long, relatively narrow features Deepest parts of ocean Most are located in the Pacific Ocean Sites where moving lithospheric plates plunge into the mantle Associated with volcanic activity Volcanic islands arcs Continental volcanic arcs An active continental margin Passive and Active Margins Continental Shelves Passive margin: broad (can be 350km wide), gentle incline,end at 140m, thick sediment layer Active margin: narrow, varied topography, end at 140m, varied sediment layer Deep-<a href="/keyword/ocean-basins/" >ocean basins</a> (half the Earth s surface) What are some features of the deep ocean floor? Oceanic Ridges Hydrothermal Vents Abyssal Plains and Abyssal Hills Seamounts and Guyots Trenches and Island Arcs <a href="/keyword/ocean-basins/" >ocean basins</a> Pacific Largest (181 x 106 km2) Deepest (avg. depth 4000 m) Surrounded by Mt. chains, trenches, volcanic island arcs Isolated from terrigenous sediments (they flow into the trenches) Old H2O Atlantic Second largest 94 x 106 km2 Mean depth 3500 m Well developed slope, rise, abyssal plains Young H2O A lot of freshwater and sediment input Indian 3rd largest (74 x 106 km2) Mean depth 3,840 m Atl Pacific ant ic Indian Ocean basin floor Mid-ocean ridge Interconnected ridge system is the longest topographic feature on Earth s surface Over 70,000 kilometers (43,000 miles) in length Twenty-three percent of Earth s surface Winds through all major oceans Along the axis of some segments are deep downfaulted structures called rift valleys Ocean basin floor Mid-ocean ridge Consist of layer upon layer of basaltic rocks that have been faulted and uplifted Volcanic activity Hydrothermal activity An oceanic ridge is a mountainous chain of young, basaltic rock at an active spreading center of an ocean. No sediment Rise ~2 km from seafloor Hydrothermal vents are sites where superheated water containing dissolved minerals and gases escapes through fissures, or vents. 350oC Play important role in chemical composition of seawater 2002 Brooks/Cole, a division of Thomson Learning, Inc. Pillow Basalts Abyssal Plains Flat featureless expanses of sediment-covered ocean floor found on the periphery of all oceans (between the continental margins and oceanic ridges) Sediment can be 1 km thick Sediment of terrestrial or shallow-water origin (very little from biological stuff sinking from the surface) Abyssal hills are small, extinct volcanoes or rock intrusions near the oceanic ridges. Seamounts are volcanic projections from the ocean floor that do not rise above sea level. Flat topped seamounts eroded by wave action are called guyots. Island Arcs, chains of volcanic islands and seamounts, are usually found parallel to the edges of ocean trenches Atolls Palmyra Island Fanning Island Ocean Sediments 4-2 Sedimentation in the Ocean Deep-sea Sedimentation has two main sources of sediment: external- terrigenous material from the land and internal-biogenic and authigenic from the sea. Red Clays: Kaolinite Chlorite Quartz Feldspar Sedimentation in the Deep Sea