Pleistocene Epoch) (30,000 years ago)-glaciers covered 29% of present land (vs. 10% today)-central Canada to Scandinavia3.drainage diversions and glacial lakes* disruption of major stream systems-Missouri, Ohio rivers displaced courses* ice-damned lakes-formed when ice blocked preglacial drainage paths4.lowering of sea level* sea level is lowered in proportion to the volume of increased ice on land* during last glacial age, sea level fell *100m* causes continental shelves to emerge as dry land (English Channel)5.deformation of the crust* weight of ice sheets causes the crust to subside-Ohio still rising-3km sheet lowers crust 1kmEvidence for Earlier Glaciationsmajor glacial ages in terrestrial sediments* layers of glacial till* soil horizons and wild-blown dust between layerssea floor evidence-marine sediment cores (uniform vs. earth)* biologic evidence-shift from warm to cold environment indicated by animal/plant habitat* ratio of oxygen isotopes-high O18/O16- more ice, glacier age-low O18/O16- less ice, interglacier ageWhat Causes Glacial Ages* shifting continents from plate techtonics-glaciation is enhanced by high latitudes-large-scale uplift of continents =* high altitudes* variations in solar radiation (astronomical theory)-variations in earth's orbit (eccentricity)-variations in earth's tilt-variations in earth's wobble (equinoxes, etc) (precession)* atmospheric factors-greenhouse gases (magnitude of changes)-Co2 and methane-dust in the atmosphere* other factors-oceanic circulation-salinity controls deep circulation-permafrost in europe and operational currents (during interglacial)-reflectivity of earth's surface-snow and ice have high reflectivity- lowers temp-solar output Chapter TwelveWind: Circulation of the atmosphere. Determined by:* convection- unequal amount of sun @ equatorial latitudes* coriolis effect- wind deflection (r-n & l-s) caused by the Earth's rotation* air moves from high to low atmospheric pressure-trade win...
