Dinosaurs Extinction Theory 12-2 Objective: Give several points on each theory and give supporting evidence by writing a short essay using the notes.

Vocabulary Extinction: there are no longer any living members of its kind or species.

# 1 Meteorite Theory Meteorite impact on Earth (K-T Impact) Large meteorites collided w/earth Threw dust and debris in the upper atmosphere

Sun completely blocked out Plants could not carry out photosynthesis-died Plant-eating dinosaurs- died Meat-eating dinosaurs-died

Evidence Layer of clay in sedimentary rock deposited at the same time as extinction Deformed grains of quartz/same as other meteorite craters Clay-layer contain element iridium/rare on earth, commonly found in meteorites

#2 Volcanic-Greenhouse Theory Clay layer caused by volcanic eruption Change in global continental movement Large amount of continental activity Dust and debris in the upper atmosphere caused by volcanic activity Change in temperatures

Sun completely blocked out Plants could not carry out photosynthesis-died Plant-eating dinosaurs- died Meat-eating dinosaurs-died

Evidence Layer of clay in sedimentary rock deposited at the same time as extinction Deformed grains of quartz/same as seen around eruption Mass animal die off

#3 Natural Extinction Gradual disappearance Slow changes in environmental Possible shifts in continents caused by plate tectonic shifts All organisms are dependent on their environments. Extinction: no more living members of a species.

Bell Work The last species of dinosaurs became extinct about _________ years ago. Louis and Walter Alvarez found a layer of clay containing ___________ and __________ that supported a meteorite-impact hypothesis. The rock record indicates that global temperatures _______ about 66 mya.

Fossils: 12-1 Objective: List the conditions that is necessary for fossils to occur by writing a description of the process. Standard: S6C1-04: Describe how the rock and fossil record show that environmental conditions have changed over geologic and recent time.

Vocabulary Fossils: remains, imprints, traces of once living organisms preserved in rocks.

Petrified remains: hard and rocklike part or all of an original materials in the remains have been replaced by minerals.

Carbonaceous film: organism is pressed under sediment layer, some heat and gases, leaving thin film of carbon residue forming an outline of the original.

Carbonization: process of chemically changes in organic material.

Mold: pores in the rock let water and air reach the shell or hard part and it then decays, leaving behind a cavity in the rock.

Cast: other sediments may fill in the cavity and harden into the rock Cast: other sediments may fill in the cavity and harden into the rock. Leaving a rock in the shape and form of the organism.

Trace fossils: evidence left behind of an organisms existence. Tracks Worm holes Burrows

Original remains: organisms or parts of organisms are found in tacked in tree resin (amber), or ice glaciers.

La Brea Tara Pits, LA, CA

Conditions Necessary for Fossils to Occur Dead organism must be protected from scavengers and microorganisms. Buried quickly by sediments. Need hard parts such as bones, shells, teeth, soft parts decay quickly or are eaten by other organisms. Usually found in sedimentary rock; heat sedimentary rock coal. Original structure of plants is lost when coal is formed. The first step is a fuel called peat.

Index fossils: species that exist for a relatively short period of time Abundant and geographically widespread Very few fossils are classified or used as index fossils Index fossils help Determines the age of rocks Dates groups of fossils Determines the types of environments

Bell Work _________ are remains or traces of once-living organisms preserved in Earth’s rocks. When minerals replace the original material of an organism, the fossil that forms is a(n) __________. A(n) _______ forms when a thin film of carbon is left behind after gases and liquids are removed from an organism.

Bell Work #2 4. Sediment that fills a cavity and hardens forms a(n) __________ of the original organism. 5. ___________ fossils are tracks and other evidence of animal activity.

Relative Ages of Rocks Principle of superposition states that in an undisturbed layer of rock the oldest rocks are on the bottom and the rocks become progressively younger (or more recent) toward the top. Relative dating is used in geology to determine the order of events and the relative age of rocks in a sequence. Unconformities develop when agents of erosion remove existing rock layers; also form when a long period of time passes without any new deposition occurring to form new layers of rock.

Angular unconformities is horizontal layers of sedimentary rock tilted and uplifted, so that agents of erosion and weathering wear them down; younger sediment layers are deposited horizontally on top of the eroded and tilted layers. Draw into notes, pages 338 and 339, a, b, c and d.

Disconformity (unconformity) horizontal rock deposited, layers uplifted, exposed, and eroded. Younger rock is deposited horizontal, the gap that is missing. Draw into notes, page 340, a, b, c. Nonconformity occurs when sedimentary rock layers from above metamorphic intrusive igneous rocks. The metamorphic or igneous rock is lifted and eroded. Sedimentary rocks are then deposited on top of this erosional surface.

Bell Work What is the principle of superposition? ______________ is a technique that determines the age of rocks as compared with one another. An unconformity between tilted and horizontal rock is a(n) _____________. A gap between horizontal rock layers is a(n) _____________________.

Absolute Ages of Rock Objective 1: Identify how absolute dating differs from relative dating. Objective 2: Describe how the half-lives of isotopes are used to determine a rock’s age.

Absolute dating is a process that uses the properties of atoms in rocks and other objects to determine their ages. Radioactive decay occurs when the number of protons in an atom changes. Half life of an isotope is the time it takes for half of the atoms in the isotope to decay. Rediometric dating is done by knowing the parent and daughter materials in a rock and by knowing the half life of the parent. The absolute age of the rock can be calculate by the geologist.

Radiocarbon dating Carbon-14 is useful for dating fossils, bones and wood up to 50 000 years. Principle of Uniformitarianism is a principle that states that Earth processes occurring today are similar to those that occurred in the past. Theory by James Hutton, advanced by John Playfair but most credit was given to Sir Charles Lyell.

Bell Work Which method of dating determines the age of a rock in years? What one of the daughter elements of uranium-238? What is the time it takes for half of a radioactive isotope to decay?