PLANET EARTH Department of Earth Planetary Sciences fall 12 Doctor Lepre Lecture 1 Review for TEST 1 Big Bang The expansion is from a hypothetical center of the universe and spreads outwardly for about 40 50 billion light years One light year is about 10 trillion kilometers or 6 trillion miles Eventually the universe will begin to contract and the process will go into reverse The contraction likely will be caused by the formation of numerous black holes that are made of some of the most dense material known to exist Black holes will pull all material in the universe into one mass and condense that mass into something that is infinitesimally small This infinitesimally small mass will eventually reach a critical mass and then a big bang will happen again And the process will repeat itself theoretically multiple times The different types of galaxies A galaxy is a collection of solar systems Pictured here is a spiral galaxy It is called such because it appears to be rotating clockwise and have arms that flail out from the center On the left we have elliptical galaxies and on the right we have spiral galaxies The Milky Way Galaxy which is the galaxy that our solar system and thus planet Earth belongs is a spiral galaxy The Milky Way is 100 000 light years in diameter with anywhere from 200 to 400 billion stars Therefore our solar system probably is about one out 300 billion solar systems in the Milk Way Galaxy Solar System Galaxies consist of solar systems Solar systems firstly are made up of a star that is in the center Secondly a solar system has heavenly bodies rotating around that star These bodies are held into orbit by the immense gravitational pull of the star Nebular Hypothesis of Solar System Formation The prevailing hypothesis is that you begin with a giant cloud of hydrogen As this cloud gains mass it builds gravity and begins to attract additional atoms of hydrogen Most of the mass is in the center and there is turbulence in the outer parts Eventually the will be dust particles made of rocks and ice that will be generated Eventually the center of the nebula condenses to a large degree and this forms the basis to a young star Around this young star a proto planetary disk forms This circular mass of dust ice and gas rotates about the gas center that is the newly formed star Over time the proto planetary disk begins to segregate into rings In the case of our solar system it is though that heavier materials like dust formed the interior rings and lighter materials like gas and ice formed the outer ones Turning back to the center of the proto planetary disk the young star at the center is very massive now As a result molecules of hydrogen collide into one another This causes thermonuclear fusion Proto Planetary Disk Planetesimals Stellar Ignition Thermonuclear fusion Thermonuclear fusion is when you have H atom H atom He atom Hydrogen consists of one proton and one electron When you combine one atom of hydrogen with another atom of hydrogen you get a new atom that has two protons and two electrons This new atom is helium The process of combining hydrogen atoms into helium release energy This energy is where stars including our sun gets its energy from Jovian Terrestrial planets Jovian planets are big planets that mainly have a composition of ice or gas The Jovian planets in our solar system Jupiter Saturn Uranus Neptune are thought to have small solid cores Jupiter Saturn are the gas giants mainly composed of hydrogen helium The other two Uranus Neptune are the ice giants and about 75 of their masses are ice consisting of water methane and ammonia The four inner planets of the our solar system are the terrestrial planets They small in size and mass Earth is the largest and most massive as compared to the gas and ice giants Each terrestrial plan has a rocky surface The surface of Venus can not be seen directly from Earth because of its dense cloud cover Lecture 2 Major and minor subdivisions of geologic time Earth s history is divided into two main parts the Precambrian and the Paleozoic The Precambrian lasted from roughly 5 billion to 540 million years ago And the Phanerozoic began at 540 million years ago and continues to today The main distinction between the two is that the Phanerozoic begins the evolution of abundant multi celled organisms with complex life histories Organism in the Precambrian were sparse and relatively simple A lot of what is known of Earth s Hadean derives from study of lunar rocks impact features The Earth was very dynamic and hot but with internal differentiation The Hadean is often metaphorically described as Hell on Earth and interpreted as a period of heavy bombardment from meteors Ancient stromatolites from the Archean represents the earliest forms of life current known The stromatolites are fossils of ancient blue green algae cyanobacteria An important contribution made by these organisms is the production of oxygen These organisms feed by photosynthesis Therefore Earth oxygenated atmosphere was likely generated by colonies of these photosynthetic organisms living in the Archean Proterozoic 2 5 billion to 540 million years ago third part of the Precambrian The Phanerozoic marks the beginning of the evolution of complex life Around continental areas within the oceans there were shallow waters that acted as breeding grounds for the numerous life of the early Phanerozoic These waters are called epicontinental seas Epi means near so epicontinental seas means seas that were just offshore from landmasses In these shallow water the Cambrian explosion of life occurred As Pangaea break ups at the beginning of the Mesozoic the ancestral Atlantic ocean begins to open up The landmasses will continue to split and drift apart until they reach their modern geographic positions The driving forces behind these changes to Earth s surface are largely found within the interior Processes like slab pull and ridge push accounted for the migration of the landmasses around the globe over millions of years At present these processes are pushing up mountain ranges such as the Himalayas and Andean mountains And these processes are also causes the earthquakes in California and other areas adjacent to the Pacific ocean The Cenozoic Era is the third and final part of the Phanerozoic It is the beginning of the modern world The continents are aligning to their present geographic positions on the globe during the early part of the Cenozoic Stromatolites Ancient stromatolites