GEOL 101 1nd Edition Lecture 25 Outline of Last Lecture I Alpine Glaciers II Landforms III Continental Glaciers IV Ice Ages Outline of Current Lecture I Weather v Climate II Earth as a System III Data IV Oxygen Isotopes Current Lecture Weather v Climate Weather Day to day state of the atmosphere with respect to temperature precipitation wind cloudiness pressure etc Variations occur on an annual cycyle seasons Generally controlled by regional changes in atmosphere temperature and moisture conditions Can locally controlled by geographic features such as mountains and lakes Climate Average prevailing weather conditions of a region throughout the year averaged over a series of years Variations occur on much longer cycles decades to tens of thousands of years Controlled by long term changes in atmosphere hydrosphere cryosphere geosphere biosphere Earth as a System The earth functions as a complex interactive system that transfers energy and matter to the five earth spheres Geosphere all the solid rock material sediment and molten rock from the surface down to the core These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Atmosphere envelope of gases held to Earth by gravity extending 100s of km upward Hydrosphere all liquid water at the surface rivers lakes oceans etc as well as groundwater Cryosphere all solid ice in the form of glaciers snowcaps sea ice permafrost etc Biosphere all living organism on planet Earth o Anthroposphere humans the parts of the environment that are influenced or modified by human activity What happens in one sphere will eventually inevitably affect aspects of the other spheres How do we know that the Earth s climate has varied throughout history The oldest direct temperature record dates back to 1659 England and the 1850s semiglobally The geologic record gives us gives us proxy indirect data about global climate has changed throughout time Widespread glacial deposits tell us about ice ages Coal beds tell us about warm tropical areas Limestones formed by coral reef environments tell us about warm shallow seas Evaporites tells us about arid conditions Type is fossils plant and animals in the rock record give us insight into climate conditions By studying and understanding the characteristics and interactions between the earth spheres today we can make inferences and reconstruct how the environment has changed through geologic time Sea floor Sediments contain fossils Oxygen Isotopes 18O versus 16O isotope ratios in marine fossils Corals exhibit growth rings similar to trees contain oxygen isotopes Ice Core Records air bubbles pollen dust volcanic ash in addition to snowfall amounts Pollen show vegetation changes in an area Historical Documents written records of events Sea Floor Sediments When marine organisms die their shells and skeletons sink to the bottom and become incorporated into the sediment The types of fossils give us indication of warm vs cold water conditions o Formainefera very sensitive to changing temperatures o There are thousands of species of forams different species like different water temperature Many marine organisms build their shells from Ca CO3from ocean water Oxygen isotope analysis Oxygen Isotopes Oxygen 16 8 protons and 8 neutrons most common Oxygen 18 8 protons and 10 neurons o Heavy Oxygen Both will form in H2O molecules o The lighter 16O will evaporate more readily then 18O and become incorporated into atmospheric moisture o Precipitation will be more concentrated in 16O o Oceans will be more concentrated in 18O Both will form in CaCO3 shells and skeletons of marine organisms During the ice ages 16O in the atmosphere precipitates as snow and ice accumulates in glaciers The glacial ice will be enriched in 16O The oceans will be depleted in 16O and enriched in 18O Organisms that make their shells and skeletons out of CaCO3 will have a higher 18O to 16O ratio During warmer periods 16O in the atmosphere precipitates as rain and makes its way back into oceans There will be more 16O in the oceans during warm periods versus during an ice age Organisms that make their shells and skeletons out of CaCO3 will have a lower 18O to 16O ratio Bottom Line High 18O Cold Low 18O Hot Corals Coral reefs grow in warm shallow waters They build their skeletons out of CaCO3 from sea water o This allows us to compare 18O and 16O ratios from them They exhibit growth rings much like trees do o Their growth rates differ in the winter and the summer o Studying modern corals and their growth rings and comparing them to corals from fossil records gives us good estimate of water temperature Ice Core Records Greenland and Antarctic ice sheets record over 400 000 years of earth history in the ice o Snowfall amounts o Air bubbles trap paleo atmosphere CO2 methane and other gas levels give us information about the composition of the paleo atmosphere Oxygen isotopes tells us about air temperature Wind blown loess ash and pollen are deposited on the ice Dust from meteorite impacts Photosynthetic ice algae cryophiles There is a direct correlation between amount of CO2 in the atmosphere and air temperature Pollen Plant species are sensitive to climate conditions o Dependent on temperature and moisture o Also dependent on altitude and latitude Pollen gets incorporated into sediment or ice by wind or water Paleobotanists can then determine which species of plants were present The fossil record also gives us a good indication of the types of plants that were present across the globe and through time Historical Data The Year Without a Summer 1816 o Mt Tambora Indonesia erupted in 1815 one of the largest eruptions in recorded history o The eruption itself was witnessed and documented by many indigenous people as well as travelers to the region o Ash and dust blocked out solar rays to the point that it caused short term global cooling Documented crop failure and food shortages in much of Europe and North America Unseasonably cool temperatures persisted for nearly a decade in some regions but were most prominent in 1816 Other forms of historical data include records like o 1st frost of the year o When crops are ready to harvest o Spring thaw o Annual flood annuals o Major droughts o Major blizards These data have been recorded for centuries for agricultural purposes throughout Europe Short and long term changes in the timing give us a proxy for changing climate conditionsMade