Presentation on theme: "Fossils and Rock Record"— Presentation transcript:
1 Fossils and Rock Record Chapter 21Fossils and Rock Record
2 VocabularyUniformitarianism- processes happening today have been happening since Earth formed. (ex. Earthquakes and volcanic eruptions)Relative-age dating- order in which geological event occur.Original horizontality- sedimentary rocks are naturally formed in flat or horizontal layers.Superposition- oldest rock layers are on the bottom and the youngest rock layers are on top.
3 VocabularyCross-Cutting Relationships- intrusions or faults are younger than the layers that they cut across.Principle of Inclusion- inclusions must be older than the rock layer that contain it.Unconformity- a gap in the rock record caused by erosion or weathering.Correlation- matching outcrops of one geographic region to another.Key Bed- a rock or sediment layer used as a marker.
4 Principles of Determining Relative Age Original HorizontalitySuperpositionCross-cutting Relationships
5 Draw a Diagram B A Intrusion Intrusions form when magma is pushed up in between cracks in Earth.IntrusionBA
7 Questions Rock layers oldest to youngest A, B, C and D- superposition. Intrusion E is younger than layer D, but older than intrusion F- Cross-cutting relationships.Rock layers A,B,C, and D are flat because of original horizontality.
8 Compare Unconformities Type: disconformityHow formed? Sedimentary rock layer deposited on top of an eroded sedimentary rock layerType: nonconformityHow formed? Sedimentary rock layer is deposited on top of an eroded metamorphic or igneous rock layer.UnconformitiesType: angular unconformityHow formed? Horizontal sedimentary rocks are uplifted and tilted then weather and erode; sedimentary rocks are deposited on top of them, but they are at an angle to the eroded surface.
9 OtherJames Hutton and Charles Lyell (Founders of Modern Geology) thought that the “present was the key to the past” – Earth works in an orderly fashion in which natural phenomenon will recur given the same set of conditions.
10 Vocabulary Drought-extended period of low rainfall. Radioactive Decay- emission of atomic particlesRadiometric Dating- process used to determine the absolute age of a rock or fossil by determining the ratio of parent nuclei to daughter nuclei within a given sample.Half-life- period of time it takes a radioactive isotope to decay to ½ of its original amount?Dendochronology- science of comparing annual growth rings in trees to date events and environmental changes.Varve- alternating light-colored and dark-colored sedimentary layers of sand, clay, and silt deposited in a lake that can be used to date cyclic events and changes in the environment.Key Bed- sediment layer that serves as a time marker in the rock record.Similar- nearly the same or alike
11 Compare absolute and relative dating Relative-Age DatingAges of rocks and events that formed them in order.MeasuresThe actual age of a rock, fossil, or other object.Absolute-Age Dating
12 Half-Life DrawingWatch the video clip on half life and draw a simple picture showing what half life is.
13 Radioactive Decay of Uranium 238 Radioactive Decay of Uranium-238 to Lead-206PercentParentElementDaughterElapsedYearsNumber of Half-LivesTime 1100Time 2504.5 billion1Time 325759 billion2Time 412.587.513.5 billion3Time 56.2593.7518 billion4
14 21.4 VocabularyTrace Fossil- imprints left by organisms that give insight as to how the organisms lived, moved, or obtained food.Index Fossil- the remains of a plant or animal geologists use to correlate or date rock layers.
15 Useful Fossils Provide information about past environmental conditions Be used to correlate rock layers from one area to anotherProvide evidence that population have evolved in response to changes in their environments.
16 PetrificationMineral solutions such as groundwater replace the original organic materials that were covered by layers of sediment with new materials.
17 CoproliteFossilized dung or feces from ancient animals.
18 GastrulatesDinosaurs had stones in their digestive systems to help digest their food.
19 Mold and CastsWhen a shell is buried, its remains decay, and sand or mud fills it in.A cast is a replica of the original organism.
20 ImprintsCarbonized imprints of leaves, stems, flowers, and fish made in soft mud or clay have been found preserved in sedimentary rock.
21 FreezingThe low temperatures of frozen soil and ice can protect and preserve organisms.
22 AmberHardened tree sap is called amber. Insects become trapped in the sticky sap and are preserved when the sap hardens.
23 MummificationMummified remains are often found in very dry places, because most bacteria which cause decay cannot survive in these places.
24 What is needed for a index fossil? It must be:It must be distinctabundantwidespreadexisted for only a short span of geologic time.+ Write down somewhere on pg. 250