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The Beginning of the Beginning • At the beginning of the universe, explosion separated gases into subatomic particles • It cooled as ions, forming hydrogen atoms, and then fusing to cause stars • Stars exploded, causing planets and asteroids to form from the remains • Galaxies of star systems orbits due to the gravitational force at the center • Collisions of galaxies formed even bigger galaxies, such as the Milky Way • One of the stars explode and matter cools into planets and the asteroid belt • Smaller planets collide to form bigger planets which are now known to day • Formed the nine planets of the solar system The Earth • Earth is the only planet with visible water and an atmosphere with a fair supply of oxygen, therefore possible for life Earth is made of several layers: • Inner core – solid iron and nickel • Outer core – liquid iron and nickel; spinning around the inner core to form an electromagnetic field • Mantle – liquid-like molten metal • Crust – consisting of 15 plates “floating” on the mantle • The Earth is 4.5 billion years old • Timeline of the Earth is separated into 3 eras: Cenozoic, Mesozoic, Paleozoic • Paleozoic: Precambrian, Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian • Mesozoic: Triassic, Jurassic, Cretaceous • Cenozoic: Tertiary, Quaternary Paleozoic (Part I) • “Dark Ages” covers the time from formation of Earth to approximately 590 million years ago • No life forms existed for the beginning of Precambrian • Many theories were made, however none were able to support their theory • First actual “animals” were trilobite, seasnail, and giant water scorpions (Precambrian, Cambrian, Ordovician, Silurian) • First plants were algae and graptolites Paleozoic (Part II) • Lungfish and Mollusk were introduced during Devonian • Land amphibians introduced during Pennsylvanian • Plants evolved into seedbearing trees, corals, and early land trees • During Permian, reptiles and early sharks appeared Mesozoic • Mesozoic is also known as the “Age of the Reptiles” • Triassic period (248 million years ago) filled with early dinosaurs and sea urchins • Jurassic period is dominated by dinosaurs, modern trees, and… birds with teeth! • In Cretaceous period, ammonite and flowering plants began to appear Cenozoic • Cenozoic period began when the dinosaurs were gone • Nobody knows what happened, but theory says that a BIG meteorite crashed onto the earth and the dust blocked out the sunlight and therefore reptiles, such as dinosaurs, could not survive • In the Tertiary period, (65 million years ago) oysters, marsupials, primate, and seabirds appeared • Introduced the wooly mammoth, the deer, and humanity in Quaternary What are Fossils? • Formerly, All minerals were called fossils • Remains or traces of an organism of a past geological age, such as a skeleton or leaf imprint embedded and preserved in the Earth’s crust Animal Fossils Traces Footprints or a marking left by the creature that is preserved in rocks Remains Bones and teeth that remained when its skin and flesh are eaten away by bacteria The Importance of Fossils • Key to unlocking the many mysteries of the past • Evidence of the existence of these ancient magnificent creatures • Also evidence for theories of how the Earth looked like millions of years ago • Skeleton can allow scientists to know how they look like • Teeth and droppings allows scientists to understand the creature’s diet Ways to Form Fossils Tar Pit – oil deposits heated by plate movements becomes a thick, gooey soup asphalt, which becomes pools of tar when surfaced. Animals can get stuck in the tar and dies Ice and Glaciers – during the last ice age, some bigger animals, such as mammoths, wooly rhinoceros, and bison are trapped in the ice and frozen. Ocean Fossils – When an animal dies, its body decays from bacteria, leaving behind a shell. The shell sinks into the sand at the bottom and over time, sediments covers it and becomes rocks Land Fossils – When an animal dies, its remains are left, and over time, sand and other sediments covers the remains and form sedimentary rocks, therefore fossilizing it. Over long periods of time, the pressure from rocks above causes it to become compressed Volcanoes – Some trees near volcanoes may be preserved since the acidic environment can kill the bacteria and also acid seeps into the piece of wood and causes it to become crystallized inside Tree Sap – Ambers are considered as fossils, even though it is not a rock. Ambers are formed when tree sap hardens over time. Many of them have animals or plants stuck in them and therefore are preserved Examples of Fossils Petrified Wood Dried Petrified Wood Opalized Wood Petrified Charcoal Amber Trilobite Planorbis Neptunia Torritella Dinosaur Eggs Dinosaur Dung Lycoptera Relative Time and Absolute Time Chronostratic Time – related to other events taking place Chronometric Time – time with a number and a measurement (quantity) Relative timescale based on four principles: Absolute time scale based on two • Different types of rocks in principles: different locations • Law of horizontality, law of • A function of the rate lateral continuity, law of of change superposition • a quantity that the • Law of cross cutting rate function is based on relation • Law of faunal succession Growth Rings on Trees •Found in the trunk and branches •One ring is grown yearly • Rings on branch plus number of years it took for the years for the trees to grow the branch equals to the tree’s age • Distance between growth rings may reflect on the environment Growth Rings on Aquatic Animals • Holocene shells have growth rings on the outside and inside of its shell • Growth rings are extremely crowded on the outside and marks from severe storms make dating difficult • Growth rings on the inside of the shell are easier to count since they are made up of dark and light bands • Growth rings are also found on corals and fishes Varves in Geographic Formation • 356 layers of stromatolites (found in fossils) are produced by cyanobacteria in one year • Tidal rhythmites are left behind from tides, caused by lunar movement • Stalactites’ length increases at a constant rate every year • Bands develop on anhydrites every season • Algae remains leave varves on the lake bottom The Atom • All matter is made of tiny building blocks called subatomic particles • They include the proton, electron and neutron, and form atoms • Different elements have different amounts of protons, neutrons and electrons • Isotopes are elements with different number of neutrons Isotopes and Radiation • Some isotopes are unstable, so unstable that, at random, protons, neutrons and electrons separate from the isotope, called radiation • Can either shed nucleus of helium atom (alpha decay), a neutron (beta decay), or energy (gamma decay) • Any element that is radioactive can be used, but those with long half lives work better • Carbon 14 is used to date anything from 50,000 years ago, while uranium 238 can be used to date things in billions of years Half-Lives • Individual radioactive atoms shed particles at random, and can’t be predicted • But groups of atoms shed particles at steady rate • As particles continue to radiate out, the atoms turn into lighter atoms called daughter particles (uranium turns into radon, radon decays into polonium, etc.) • The time it takes for half of all of mass of atoms to radiate into lighter atoms is its half-life History of Radioactive Dating • First to discover radiation was Henri Becquerel, in 1896 • He and Ernest Rutherford first used radiation to date rocks in 1907 • The idea was further implemented after WWII, when radiation was used for nuclear testing • As measurements of both decay and half lives improved in the 1950s, measurements became more accurate • Became a way to test everything from rocks to fossils, and let archeologists and geologists see into the past Tools and Processes • Many radioactive materials exist naturally in materials: potassium is usually found in lower sedimentary rocks, while uranium is found in • Mass spectrometer, Geiger counter are used to measure the level of radioactivity • Number of particles being emitted is compared to half-life curve to determine how old something is • Also can tell by number of daughter atoms, such as seeing how many uranium atoms have turned into radon • Another method involves spontaneous fission and the radioactive tracks it produces ERROR • Unfortunately, all naturally occurring rocks are subject to contamination, so dating can be inaccurate • Problems with scientific instruments: as tools get better, so do results (in 1950, avg. result had 25% error rate, modern tests have 5% error rate) • Always strange results, like a Rb-Sr dating giving 34 billion years Plate Tectonics • Alfred Wagener suggest that 200 million years ago, all continents were together, called Pangaea • However, his theory was ignored until the 1960s Evidence: • Plant and animals which would not have survived in the sub zeros found in Antarctica • Fossil of dinosaurs found in two places across the Atlantic Ocean • Realize Earth’s surface is not one big piece • Many smaller pieces called tectonic or lithospheric plates, moved by the slow convection currents in the upper mantle Rocks in mantle is very hot Heated rocks tends to rise, when some cooler rock moves in to take its place Forms convection current Pangaea • Shores of the continents fit together like a jigsaw puzzle, as Wegener also did • Pangaea means “all the Earth” in Greek • Existed in the late Carboniferous times • Formed from three smaller continents, which later became two: Laurasia,and Gondwana Pangaea is split into two parts, Northern Pangaea and Southern Pangaea, called Laurasia and Gondwana respectively Laurasia = North America + Eurasia (Europe) Gondwana = South America + Africa + Australia + Antarctica + Asia Mid-Ocean Ridge • Example: Mid-Atlantic Ridge • A rift valley runs down middle, meaning separation • Along the valley, molten rocks flows out • Forms with two plate moves apart, causing molten rocks to rise • Atlantic Ocean is getting bigger as the sea floor spreads Trenches • There are two types of plates, oceanic and continental • Oceanic plate is heavier than continental plate • Oceanic plate slides under the continental plate • Ocean floor is pulled under by the plate • Forming the lowest parts of the ocean floor, including the Mariana's Trench Mountains • Two continental plates of similar density collides with each other, one would not slide under • Crash into each other, like two cars running at full speed at each other • Cause bottom half of the plates to go down and top half to ruse up into sharp mountains • One great example of this is the Himalayas Weathering • Chemicals in rocks are unstable in damp, oxygen-rich atmosphere • Used to the hot and high pressure surroundings • This reaction is called weathering • Temperature also cause weathering • Sun heats up rocks during the day, and the cold of the night causes the rocks to crack Erosion • Erosion is process where material in solution and loose rock fragments are removed from the original location and transported to another place Examples of erosions: • Ice • Wind • Water (waves and rain)