Geology Notes 1 Test on Tuesday a Know time scale Mostly Phanerozoic b COME PREPARED AND STUDY 2 Cenozoic cooling trend a Mesozoic warm trend b 2 periods Paleogene and Neogene c Multiple epochs in Cenozoic i Pleistocene ii Halocene 3 Milankovitch cycles a Earth s axis wobbles over 26 000 years affecting the amount of solar radiation received at the poles b Orbital eccentricity Earth s orbit changes from more circular to more elliptical over about 100 000 years varying the amount of solar radiation received c Angle of tilt of Earth s axis i Currently about 23 5 degrees ii Causes the seasons iii Varies over about 41 000 years changing length of days and amount of solar radiation received at the poles d Correspond well to glaciation episodes which have occurred every 100 000 years over the past 600 000 years 4 What are other things that effect climate a Non Milankovitch factors in global climate change i Reflectivity of the Earth 1 If Earth s albedo increased snow cover cloud cover or dust in the atmosphere temps would decrease due to the reflection of solar radiation into space ii A decrease in CO2 would lead to cooling iii Conversely an increase in atmospheric CO2 would cause warming 1 Because it s a greenhouse gas iv Plate tectonics a continent must lie on or near a pole for snow to build up to form a glacier v Plate tectonics formation of Isthmus of Panama diverted the Gulf Stream northward about 3 5 million years ago 1 Warm moist air associated with this ocean current led to increase in snowfall in northern areas and development of continental glaciers vi The impact of human activities such as increased burning of fossil fuels and the associated buildup of greenhouse gases 5 The Little Ice Age a Cold spells recurred periodically into Holocene b Lasted from 1540 1890 temps were several degrees cooler than today c Loss of harvest famine food riots and warfare in Europe d Heightened volcanic activity occurred e Volcanic ash and aerosols in the atmosphere caused temperatures to drop 6 What was life like a During Cenozoic Mammals dominate Age of Mammals b Adaptive radiation near beginning of Cenozoic resulted in mammals as diverse as bats and whales c Appearance of Homo Sapiens i Appearance and evolution of primates to ancestors of humans by onset of Neogene ii Homo Sapiens appeared during Pleistocene 7 We know more about Cenozoic life than any other time span Why a Fossils are better preserved less time to be destroyed b Stratigraphically highest usually more accessible for study c Cenozoic fossils more closely resemble today s life forms 8 Causes of biologic changes a Tied to i Environmental Change 1 Cooler and drier climate led to expansion of the grasslands Influenced the evolution of herbivorous mammals 2 ii Geographic change 1 Continental breakup result of plate tectonics stimulated biological diversity 9 Recovery from the Extinctions a Late Cretaceous extinction left diversity low b Recovery was rapid diversity quickly climbed to a much higher level than ever before 10 Eocene Oligocene boundary a Slight drop in diversity due to worldwide cooling 11 Cenozoic plant life a Flowering plants or angiosperms i Appeared during cretaceous ii Became dominant land plant during Cenozoic 12 Grasslands expand and mammals respond a Grasses flowering plants commonly eaten by grazing mammals became widespread during Miocene b Expansion of the grassland across plains of North America and other continents related to cooling and drying of global climate c Mammals evolved in conjunction with spread of grasslands 13 Mammals a Characteristics i Seven neck vertebrae ii Appalachian iii Large braincase 14 Early mammals Insulation by hair aided survival by preventing heat loss Mammary glands are modified sweat glands a First mammals small b c d Tooth patterns suggest early mammals ate insects e Skulls show that smell and hearing were well developed suggesting they were nocturnal 15 Rodents a Probably outnumber all other mammals b Have adapted to many habitats i Partially aquatic desert dwellings and tree dwelling c Also includes hamsters gerbils guinea pigs and chipmunks d Teeth i Specialized for gnawing and nibbling ii Lack canines 16 Development of Panamanian land bridge 3mya led to migration of mammals between north and south America 17 Bering land bridge a Between north America and Eurasia existed during Pleistocene b Camels horses mammoths and other migrated across c Also used by early humans to enter north America at least 14 000 years ago 18 Extinction of the Large Pleistocene Mammals a 17 000 years ago during last glaciation North America supported many types of large mammals i odd toed ungulates ii even toed ungulates iii many others b Most large land mammals began to go extinct about 8000 years ago c Why 2 hypotheses i Human hunting and predation ii Climate change associated with global warming at the end of the last Ice Age 19 Regressive periods associated with glaciation and vice versa 20 KNOW TIME SCALE THIS IS A HISTORY CLASS a Build up knowledge before studying i Know Phanerozoic ii Know last two epochs b Part of exam will be fill in time scale c Tell whether this event happened during Paleozoic Mesozoic or Cenozoic