Chapter 4 Test Review What are fossils? What is a petrified fossil? The time it takes for half of the radioactive atoms to decay Used to determine the absolute age of rocks. The preserved remains or traces of past organisms An type of organism which no longer exists on earth A fossil formed when minerals replace all or part of an organism 88% of earths history Allow scientists to infer the Earth’s age A thin coating of Carbon left on a rock Footprints All continents joined together about 250 million years ago How geologists divide Earth’s history When rock layers are turned over completely When atoms break down to form other atoms Describe past environments and history of life Geologic processes that change Earth today also changed Earth in the past Mold is the outside shell, cast is the solid copy When an organism becomes trapped in stick tar or resin Radio active element used to date remains of organisms A plentiful, short lived fossil used to date rocks Age related to other rocks and age since the rock was formed The youngest rocks are on top and the oldest on the bottom What are fossils? What is a petrified fossil? How have fossils helped scientists? What does extinct mean? What does half-life mean? What is radioactive decay? How does radioactive dating help scientists? What is uniformitarianism? What is folding? How do moon rocks help scientists determine the Earth’s age? The pre-Cambrian era covers what percent of earth’s history? What is a carbon film? What is a trace fossil? What is the law of superposition? What is the geologic time scale? What is Pangaea? How do we get preserved remains? What is Carbon-14 used for? Compare/Contrast molds and casts. Compare/contrast relative and absolute age of rocks. What is an index fossil?

What are fossils? The preserved remains or traces of past organisms What is a petrified fossil? A fossil formed when minerals replace all or part of an organism How have fossils helped scientists? Describe past environments and history of life What does extinct mean? An type of organism which no longer exists on earth What does half-life mean? The time it takes for half of the radioactive atoms to decay What is radioactive decay? When atoms break down to form other atoms How does radioactive dating help scientists? Used to determine the absolute age of rocks. What is uniformitarianism? Geologic processes that change Earth today also changed Earth in the past What is folding? When rock layers are turned over completely How do moon rocks help scientists determine the Earth’s age? Allow scientists to infer the Earth’s age The pre-Cambrian era covers what percent of earth’s history? 88% of earths history What is a carbon film? A thin coating of Carbon left on a rock What is a trace fossil? Footprints What is the law of superposition? The youngest rocks are on top and the oldest on the bottom What is the geologic time scale? How geologists divide Earth’s history What is Pangaea? All continents joined together about 250 million years ago How do we get preserved remains? When an organism becomes trapped in stick tar or resin What is Carbon-14 used for? Radio active element used to date remains of organisms Compare/Contrast molds and casts. Mold is the outside shell, cast is the solid copy Compare/contrast relative and absolute age of rocks. Age related to other rocks and age since the rock was formed What is an index fossil? A plentiful, short lived fossil used to date rocks