GEOL 101 1nd Edition Lecture 3 Outline of Last Lecture I Intro to Geology II Science and History to Geology III Geologic Time Outline of Current Lecture I Geologic Time II Scientific Method of Inquiry III Earth s Internal Structure Current Lecture Principals of Relative Geologic Time Law of Superposition When looking at rocks and sediment layers the oldest rocks are at the bottom and in turn the youngest rocks are on top Principle of Fossil Succession Fossil organisms in rocks succeed each other in a definite and determinable sequence The reason any time period can be recognizable by the fossil The amount of years in the geologic time era can involve millions or billions of years Most of Earth s time has been categorized in the Precambrian era Knowing the era and its time in years is important because formations and processes by Earth happen slowly and gradually Since science assumes nature is consistent and predictable the goal is to find patterns then use that information to predict the future Geologists like most scientists collect their information from observations and data measurements Although there is always a degree of error in these processes it is still important to use for scientific theories Hypothesis An educated guess e g Life on Mars Theory An explanation that has been tested many times and is widely accepted by the scientific community to best explain certain facts e g Plate Tectonics 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 Scientific Law A universal fact that seems to always be true e g Law of Gravity Earth has 5 spheres 1 2 3 4 5 Hydrosphere water Atmosphere gases Cryosphere ice Biosphere life Geosphere rocks Earth is a planet with interacting spheres with many parts that are connected with one and other One can affect the other For example A volcano eruption releases CO2 into the air then the CO2 may result in global warming melting glaciers and ice then melted ice flows into the ocean changing the salt water ratio which affects water life The Earth s system is almost always powered by the sun which energizes external processes in the atmosphere hydrosphere and the surface Another source of power is Earth s interior It is mostly heat from the formations of Earth and radioactive decay and produces volcanoes earthquakes and mountains The Rock Cycle is the transformation of one rock to another It shows the processes materials on Earth can change both inside and outside of the Earth This cycle can skip steps or skip forming into a certain rock Igneous Molten rock Sedimentary Loose weathering and sediments that get packed into a solid rock OR formed by precipitation out of a solution Metamorphis Rock from heat and pressure Magma is the same as lava Magma is underneath the surface and lava is above Molten rock Cooling and Crystalizes Igneous rock Igneous rock Weathering and Compaction Sedimentary rock Sedimentary rock Heat and Pressure Metamorphic Rock There are many shortcuts to the process Planet Earth from the Beginning Most accepted theory of Earth s origin is The Big Bang Theory a huge explosion that made all matter go outward The debris came together ad cooled off to form galaxies and stars The Nebular Hypothesis says our galaxy formed from a cloud of matter at the same time Since radioactive decay produce heat the material began to melt iron and nickel The liquid metals sank to the center and formed a dense core Materials like silicon and aluminum went to the surface and formed the crust Three main layers defined by composition Crust Very thin rocky material o Continental Crust Thick high amounts of silicon and aluminum o Oceanic Crust Much thinner high amounts of calcium sodium and iron Mantle Solid rocky shell Composed of peridotite that has high amounts of magnesium and iron Core Innermost part of the Earth High amounts of iron nickel Internal Structure Five main layers based on physical properties Lithosphere Rock Makes up crust and plate tectonics Asthenosphere Weak Free to move independently Mesosphere Middle Lowest layer of mantle Rocks are very hot and can flow around Outer Core Liquid iron nickel Generates magnetic field Inner Core Solid iron nickel Really strong and dense Continents sit higher because they are made up of less dense material while ocean basins are denser causing them to sit lower Continental Deep Ocean Basins Shelf Abyssal Plains Slope Oceanic Trenches Rise Sea Mounts Ocean Ridges