Chapter 18: Amazing Ice: Glaciers and Ice Age Glaciation and Global Warmingo 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 Ageo Areas of erosion and deposition.o US = mainly depositionalo Max ice thickness = 3-4 kmo 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 leveldropped 85 meters. Climate Change and Ice Ageso 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 TECTONICSo Polar continents allow buildup of land iceo When there are fewr continental bodies on the poles, the ice cannot build upo Short-Term Fluctuations (Glacial and Interglacial Periods within ice ages) Eccentricity of orbit – earth’s path around the sun changes from a circularto elliptical orbit (100,000 year cycle)- low eccentricity : more circular- high eccentricity : more elliptical Tilt of the Earth’s axis of rotation varies from 21.5 to 24.5 degrees (41,000year cycle)- Reason for seasons- More tilted = extended dark times 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- Shorter ones every 20,000 yearso Shorter-Term Fluctuations- Volcanism- Sun spot activity- Reflectivity of Earth’s surface- Disruption of thermohaline currents due to decreasing evaporation & increasing salinity Climate Change and Ice Ageso 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 1 ring = 1 year Certain trees are only found in certain areaso Ice Core Basics Incorporation of Air in Polar Ice Records of CO2, CH4, and N20 The Earth’s Glacial Historyo Precambrian (~2.2 billion years ago) Evidence – layer of tillliteo Permian (~245-286 Ma ago) Striations on bedrock + tillites found on Australia, S. America, India and Africa Evidence of Pangeao 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 Glaciationo Changes in Sea Level Sea level falls during glacial periods Sea level rises during interglacial periodso 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? Yeso How much? 33 degrees Celsius Is humanity contributing to the warming of the Earth? In other words are we causing global warming?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 atmospherewas 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 Tectonicso 95% of energy from earthquakes affect narrow zones along the boundaries What causes earthquakes?o Earthquakes : vibrations of the ground created by the sudden release of strain energy accumulating in deformed rocks.o Where does the strain come from? Strain : the accumulation of stress energy Types : elastic, brittle, plastico Earthquakes can be on all fault types What is an earthquake?o Fault : crack in Earth where slip occurso Earthquake : vibrations produced during slippage along a faulto Earthquake focus : fault slip locationo Earthquake epicenter : point on the surface directly above the focus May not even feel anything (like eye of a