Intro Ode to Joy Logistics The Quarry Life on Mars Earth-- the Special Planet The Gaia Hypothesis Earth System Science Welcome slides and Beethoven
Class is designed for the beginning science major first class in the Earth Sciences major required by other depts (Environmental, for example) Satisfies Quantitative requirement (+natural science requirement) rigorous class designed to give you foundation to continue in the Earth and physical sciences Reason for all to take this class is to help be good Earth citizen Alfred Hochstaedter ahochstaedter@earthsci.ucsc.edu 459-5228, EMS C470A TR 2-3, by appt Please come see me Requirements Books -- Text and lab book + lab manual Copy Center = main floor Communications Text book is not mandatory; could use any introductory text. Lab books are mandatory. Field trip -- Saturday Nov 9 -- see the things we're talking about optional don't drop the class if you can't go -- see me instead Home works are the quantitative aspect of this lab explain notation on syllabus First one defines working class list -- hand it in or be dropped! Hand Lens -- for those of you in the labs Tests -- will come ~90% from lecture and ~10% from the book. Take roll confirm those that have registered. Get idea of how many non-registered people show up. Labs -- strongly encouraged Learn more in labs (active) than listening to lecture (passive) Labs start next week. No labs this week. Introduce TAs -- Kelly MacGregor Josh Stein Paul Lawlar Mon 9:30-12:30 (Kelly) fewest students -- cancel Mon 12:30-3:30 Josh(?) Wed: 2-5 Paul Wed 6-9 Kelly Th 8:30-11:30 Paul Th 2-5 Kelly Get Started!!! Earth Sciences is important because it educates us and enables us to be good Earth citizens. --Understanding the Earth helps us understand and plan for natural disasters such as volcanic eruptions and earth quakes. --It helps us understand the formation, distribution, and abundance of natural resources: oil, gas, iron for steel, Al for ceramic, building materials. Everything we use comes ultimately from the Earth. --It helps satisfy our curiosity as to how the natural world around us works. Why do beaches look different on the east and west coasts? --Environmental Geology -- What are the geologic hazards for various building sites? --We will find that the Earth is dynamic. Interconnections are everywhere. --- --Every rock tells a story about the history of that part of the Earth, and provides information about the current state, and perhaps future of the planet. --Geology is an outside science. It something one does, not reads about or passively absorbs like a listening to a lecture. Geology as an Observational Science Quarry Trip --Look at rocks. What kind? What story do they tell? --Can't do it. That is the objective of this class. --That skill is what you'll walk away with. --Marble -- CaCO3. Originally shells and bones of living organisms in a warm shallow sea. -Formed limestone. --Metamorphism. perhaps due to depth of burial, perhaps due to collision and emplacement during tectonic events, perhaps related to intrusion of plutons (roots of cascade volcanoes. --Large grain size. not good for cutting or carving. Good for lime (Ca) for cement --This area is a quarry. The rock was mined for the Ca to make cement. --Important resource in the late 1800s. CaCO3 = CaO + CO2 upon heating --Responsible for the development of this area and the historic buildings and kilns at the entrance to campus. --Also responsible for topography -- sinkholes and deep canyons --CaCO3 disolves in acidic water --Buildings can fall into developing sinkholes, as happenned at applied science --Plays a role in temperature control of the planet. CO2 in rocks rather than atmosphere, where it would increase T because CO2 is a greenhouse gas. --We have told a story. --Deposition in sarm shallow seas -- an environment very different than today --metamorphism due to large geologic events collisions-plutonism --Uplift due to later tectonic events -- something happenned --influence on social history -- mining for lime -- economic development of region --influence on development -- sinkholes -- problems in building --Satisfies our curiosity of our natural surroundings --Where it comes from, why it looks the way it does. Life on Mars Big story this summer. Evidence found in martian meteorite for long-ago life on Mars Evidence by no means conclusive; better to say: observations in Martian meteorite interpreted as formed by biological process Emphasize not life today, but millions of years ago. Evidence was found in carbonate globules in cracks of an igneous (formed from magma) meteorite. The evidence includes: 1) visiual evidence: ovoid and elongate features that resemble bacteria fossils in Earth rocks, although the ones from Mars are 100 times smaller, about 100th the diameter of a human hair. 2) occurance of a certain kind of carbon-bearing molecule called "polycyclic aromatic hydrocarbons" or PAHs for short. These molecules are formed by the breakdown or reaction of other carbon-bearing molecules. Since carbon forms the backbone (so to speak) of most biologic material, PAHs ccould indicate the presence of biologic activity. 3) The presence of a peculiar group of minerals that should not precipitate together by inorganic processes. It is a *disequilibrium* assemblage. Specifically, the minerals include Fe-oxide (magnetite), and Fe-sulfide (something similar to pyrite or fool's gold). These minerals do precipitate together in boigenic systems. Individually, none of these observations would be interpreted as indicative of life, but together, they do cause people to take notice. The visual evidence is actually the most provocative because it claims they are fossils McKay himself said, "Our favored interpretation is that these are in fact microfossils from Mars. That is an interpretation; we have no indipendent evidence." This case is an excellent illustration of the scientific method. Observe -- hypothesis --- observe and test -- improved hypothesis more testing -- more testing -- theory -- more testing -- improved theory -- more testing -- more testing -- law compare Life-on-Mars idea with Evolution, tectonics, etc... What is the chronologic history of this meteorite? 4.5 billion years ago -- solidified from magma 3.6 billion years ago -- meteorite impact shattered the rock leaving fractures where the evidence was found. about 16 million years ago -- another meteor impact launched the rock into space where it wandered for 16 million years 13,000 years ago -- became buried in the Antarctic ice cap. How do we know it from Mars? The isotopic composition of internal volatiles resembles those measured on the Martian surface by Viking Landing in 1976(?) What about life today on Mars, or other planets? Must discuss "life as we know it" "Life as we know it" 1) needs moderate temperatures (for liquid water). Evidence of water is often taken as evidence for the possibility of life. 2) Changes environment around it plants give off oxygen as they repirate First thing to do is look at the planets. they look different. Earth is blue, whereas the others (Mars and Venus) are not. The atmospheres are different too. Earth has Oxygen whereas others are primarily CO2. Compare using Broecker's and Lovelock's tables temp maily dependent on 1) distance from sun, and 2) amount of CO2, a greenhouse gas, in the atmosphere If CO2 in atmosphere, it warms the surface temperature of the planet. Mars and Venus have much more CO2. Earth's temperature much cooler than it should be with CO2. Earth has oxygen in atmosphere; Mars and venus do not. Why abundant O2 and no CO2 on Earth? These abundances are out of equilibrium. Think about what would happen during a fire.-- all O2 depleted during burning. Answer is life (the biosphere). Plants use CO2 and contribute O2 to the atmosphere. Most Carbon contained in carbonates (like those at the quarry) and in living things. Life causes chemical composition of atmosphere to be out of equilibrium Dis-equilibrium atmosphere -- a hallmark of planets with life? So argures James Lovelock, the originator of the Gaia Hypothesis -- not very popular with proponents of manned space expiditions designed to look for life. The Gaia Hypothesis: The physical and chemical condition of the surface of the Earth, of the atmosphere, and of the oceans has been and is actively made comfortable by the presence of life itself. This is in contrast to the conventional wisdom which held that life adapted to the planetary conditions as it and they evolved their seperate ways. Venus is too hot because of abundance of CO2 in the atmosphere. Mars is too cold because CO2 and H2O froze and provide no geenhouse warmth. On Earth, biosphere keeps CO2 out of atmosphere and temperature appropriate for hydrosphere. In addition, biosphere keeps O2 in atmosphere, which enables weathering. and formation of sediments and rock cycle. The Gaia Hypothesis has lead to New Age beliefs that the Earth is alive and can actively predetermine its temperature. This is NOT what Lovelock ever suggested or imagined. In the Scientific community, These ideas of complicated interactions between the biosphere, the hydrosphere, the atmosphere, and the lithosphere (rocks) have been termed "Earth System Science", which we will discuss over the next few class periods.