Presentation on theme: "Section 3.1 Vocabulary to know:James Hutton Uniformitarianism Catastrophism Charles Lyell."— Presentation transcript:
Section 3.1 Vocabulary to know:James Hutton Uniformitarianism Catastrophism Charles Lyell
James Huttons New Idea Came up with a theory in 1788… –Uniformitarianism Geologic processes happening today also happened in the past Seems obvious, but actually sparked controversy
Catastrophism Vs Uniformitarianism Not everyone liked Huttons ideas… Catastrophism: –States that geologic change occurs suddenly Uniformitarianism lost the debate until Charles Lyell proved Hutton to be right…kinda…
A Happy Medium Most geologic processess follow Huttons theory of uniformitarianism … But sometimes Catastrophism does occur –Asteroids Meteor Crater in Arizona
Section 3.2 Vocabulary to know:Relative age Law of Superposition Principle of horizontality Principle of cross- cutting relations Index fossil
What is their age?
?????????? Dont know their absolute age Relative age- –The age of an event or object (person) in relation to other events or objects (people) –In other words, you put things in order oldest to youngest… …Or youngest to oldest
What can we learn about time from this picture?
You can learn a lot! Until the 1900s we couldnt get absolute ages for fossils… We had to assign things based on the order that they occurred Law of Superposition- –Sedimentary rocks form in layers –Oldest layers on the bottom… –…Youngest on the top
Principle of original horizontality Sedimentary layers are nearly horizontal when deposited… Those that are not, have been deformed by movements of Earths crust
Principle of crosscutting relations Geologic features, such as faults, and igneous intrusions are younger than the rocks they cut through
Whats the oldest layer?
Put these in order from oldest to youngest… Youngest _____ Oldest
Index fossils Index fossil- –Fossils of organisms that were common, lived in many areas, and existed only during specific spans of time Fossil found in specific rock layer MUST have lived during that time
Life cycle of a fossil…
Bad index fossils…Why? Shark Crocodile
Section 3.3 Vocabulary to know:Absolute age Atom Element Isotope Atomic number Atomic mass Radioactivity Half-life Carbon-14 dating
Ok great… But how do we figure out the actual age of fossils? Absolute age- –The actual age of an object or event To figure out absolute age you have to take a look at atoms… …more specifically, the isotopes of those elements made up of atoms Absolute
A riddle to show me you understand… There are two goat herders… One named Jeremy, and the other named Decker Jeremy says to Decker, Why dont you give me one of your goats so that we have the same amount? Decker responds with, No, why dont you give me one of your goats so that I have twice as many as you? What is the relative amount of goats that each person has? What is the absolute amount of goats that each person has?
Atoms Atom comes from the Greek word atomos… –…which means: unable to cut Atoms are made up of: –Protons (In the nucleus) –Neutrons (In the nucleus) –Electrons
Elements Element- –a pure substance that consists entirely of one type of atom –Make up everything in the universe –Atomic number- number of protons. –Atomic mass- protons + neutrons. Why is it 4.003, and not 4.0?
Isotopes Isotopes are identified by their mass number. Protons are constant…but sometimes there can be more neutrons than protons.
Radioactivity… Some isotopes are unstable –Meaning that they only exist for a little while before they change (Breakdown) into something else (more stable form) Certain isotopes always change (Break down) into something else (more stable form) at the same rate
Use radioactivity as a geologic clock Half-life- –Length of time it takes for half of the atoms in a sample of a radioactive element to change from an unstable form into another form Different elements have different half- lives –Fractions of seconds –Billions of years ParentDaughterHalf-life (years) Thorium- 232 Lead billion Uranium- 238 Lead billion Beryllium -10 Boron million Carbon- 14 Nitrogen
Half-lives Rate of change from one element into another is measured in half-lives Breaks down at a constant rate
Carbon-14 dating Live organisms take in C 14 –Half-life = 5730 years When an organism dies it no longer takes in C 14 C 14 breaks down into N 14 at a constant rate By measuring the half-life we can figure out when the organism died
Section 3.4 Vocabulary to know: Fossil Original remains Ice (Original remains) Amber (Original remains) Tar (Original remains) Sedimentary rock (Fossils) Molds Casts Petrified wood Carbon films Trace fossils Tree rings Ice core
How do we know about the past? Rocks and fossils! Fossil- –Traces or remains of living things from long ago… Fossils exist in many forms- –Hard animal remains (shells, bones, teeth, etc.) –Impressions on rock –And sometimes…
You actually find the organism Original remains- –Fossils that are the actual bodies or body parts of organisms –Found in substances that keep out air and tiny organisms Very important because they give DIRECT evidence that is undisputable
How are original remains preserved? Ice- –Ice fields in Siberia and Alaska contain 10,000 year old mammoths and rhinos –Bones, muscle, skin, and even hair in place
How are original remains preserved? Amber- –Tree sap traps insects within it –Tree gets buried and this sap turns into amber
How are original remains preserved? Tar- –La Brea tar pits trapped animals from the past –Saber- toothed cats and other animals have been preserved
How do fossils form? The organism must be preserved before it decomposes –Hard parts (bones, teeth, tree trunks, etc) decompose slowly –Soft parts (muscles, skin, etc) decompose fast Most fossils are the hard parts of organisms
Where do rock fossils form? Sedimentary rock- –Formed from sediments being compacted and cemented together Sometimes the sediment builds up around plant or animal remains If sedimentary rocks are changed by heat and pressure… …the fossil is usually destroyed
Fossils in rocks Molds- –A visible shape that was left after an animal or plant became buried in sediment and then decayed away Casts- –When a mold becomes filled with minerals and preserves the shape of the original organism
Fossils in rocks Petrified wood- –Tree is covered in sediments… –…water with minerals seeps into the tree… –…minerals end up producing a cast of the tree Carbon films- –Sometimes the Carbon from an organism is left behind as a visible layer Trace fossils- –Not parts or an impression of an animal, but some other evidence Ex: footprints
How do we know what the environment was like in the past? Tree rings- –Width of the tree ring depends on how much the tree grew that year –Thin ring = dry year –Thick ring = wet year Lots of growth during wet years Ice cores- –Analyze air trapped within the ice to see how the atmosphere has changed –Can test ice from as far back as 530,000 yrs ago