Chapter 18 Amazing Ice Glaciers and Ice Age Glaciation and Global Warming o How are these related What is weather day to day variation in the atmospheric conditions What is climate long term average of all weather events including the variability Continental Glaciation The Last Ice Age o Areas of erosion and deposition o US mainly depositional o Max ice thickness 3 4 km o During the last ice age the sea level drops Pulls water from ocean and locks it up as ice in glaciers o Land surface expanded 18 000 years ago during the last ice age because sea level dropped 85 meters Climate Change and Ice Ages o Long Term Causes Cause of Ice Age Large landmasses at or near poles Land surfaces of relatively high elevation Nearby oceans to provide moisture as snow PLATE TECTONICS o Polar continents allow buildup of land ice o When there are fewr continental bodies on the poles the ice cannot build up o Short Term Fluctuations Glacial and Interglacial Periods within ice ages Eccentricity of orbit earth s path around the sun changes from a circular to elliptical orbit 100 000 year cycle more circular more elliptical varies from 21 5 to 24 5 degrees 41 000 low eccentricity high eccentricity Tilt of the Earth s axis of rotation year cycle More tilted extended dark times Reason for seasons Precession Earth s axis wobbles like a top 23 000 year cycle More precession extended dark times Milankovitch Cycles Moderate term fluctuation glaciation every 100 000 years o Shorter Term Fluctuations Volcanism Shorter ones every 20 000 years Sun spot activity Reflectivity of Earth s surface Disruption of thermohaline currents due to decreasing evaporation increasing salinity Climate Change and Ice Ages o Other global effects include the circulation of water in the oceans o Information about glacial periods can be derived from fossils in sediment from the ocean floor o Isotopic Record of the Ice Volume The global ice volume increases during glaciations Ice on the continents is enriched in Oxygen 16 Water in the oceans is depleted in Oxygen 16 Calcareous ooze from the ocean floor contains a record of these isotopic variations Calcite in calcareous calcite is oxygen calcium and nitrogen o Dendrochronology looking at trees rings fossils species etc Climate data back to about 8K 10K years ago Certain trees are only found in certain areas 1 ring 1 year o Ice Core Basics Incorporation of Air in Polar Ice Records of CO2 CH4 and N20 The Earth s Glacial History o Precambrian 2 2 billion years ago Evidence layer of tilllite o Permian 245 286 Ma ago Striations on bedrock tillites found on Australia S America India and Africa Evidence of Pangea o Quaternary 1 8 Ma ago cooling began about 50 Ma ago now suggest glaciation began 3 Ma ago N American Ice Sheet stripped soil sediment and bedrock Glacial max 20K years ago Ice Sheet began retreating about 12K years ago interglacial period Additional Effects of Glaciation o Changes in Sea Level Sea level falls during glacial periods Sea level rises during interglacial periods o Changes in Landscape The Great Lakes The Channeled Scablands What is the greenhouse effect o What gas es help increase this effect CO2 methane H2O vapor o Does this have an effect on Earth s temperature Yes o How much 33 degrees Celsius global warming Is humanity contributing to the warming of the Earth In other words are we causing o Probably the basic definition of global warming is that Earth s temperature is rising It does not differentiate between natural and man included effects Is the climate change that is recorded really significant o This is a highly debated topic The last time there has been this high of concentration of CO2 in the atmosphere was about 40 50 million years ago In the geologic past there have been times that greatly exceeded this concentration but it is the rate that the CO2 is increasing which is troubling Chapter 8 Earthquakes Why should you be concerned with earthquakes o They can kill us Earthquakes and Plate Tectonics o 95 of energy from earthquakes affect narrow zones along the boundaries What causes earthquakes o Earthquakes energy accumulating in deformed rocks vibrations of the ground created by the sudden release of strain o Where does the strain come from the accumulation of stress energy elastic brittle plastic o Earthquakes can be on all fault types Strain Types What is an earthquake crack in Earth where slip occurs o Fault o Earthquake o Earthquake focus o Earthquake epicenter fault slip location vibrations produced during slippage along a fault point on the surface directly above the focus May not even feel anything like eye of a storm