fossils Relative age of rocks 10 10 10 10 10 20 20 20 20 20 30 30 30 30 30 40 40 40 40 40 50 50 50 50 50 Radioactive Geological dating time scale Early Earth Question 1 - 10 • are the preserved remains or traces of living things. Answer 1 – 10 •fossils Question 1 - 20 • Fossils provide evidence of Answer 1 – 20 •how life has changed over time Question 1 - 30 • a hollow area in sediment in the shape of or part of an organism. Answer 1 – 30 • mold Question 1 - 40 • evidence of the history of life and past environments on Earth is called Answer 1 – 40 • The fossil record Question 1 - 50 • List the steps of how fossils are most commonly formed Answer 1 – 50 • Organism dies • Organism is buried by sediment • Sediment hardens and preserves fossil Question 2 - 10 • The number of years since the rock formed Answer 2 – 10 • absolute age Question 2 - 20 • In horizontal sedimentary rocks, the oldest layer is at the bottom and the newest layer is on the top and determines the relative ages of rocks Answer 2 – 20 • The Law of Superposition Question 2 - 30 • the surface where new rock meets up with a much older rock surface. Answer 2 – 30 • Unconformity Question 2 - 40 • What is an index fossil? Answer 2 – 40 • A fossil that is widely distributed and represents a type of organism that only existed briefly Question 2 - 50 • Index fossils are useful because- Answer 2 – 50 • tell the relative ages of rock layers by how they occur Question 3 - 10 • As elements break down over time they release particles and energy in a process called Answer 3 – 10 • radioactive decay Question 3 - 20 • How fast or slow the radioactive elements decay is always constant (never changing) and the rate of decay is called Answer 3 – 20 • half-life Question 3 - 30 • Very useful in dating rocks because it has a long half-life Answer 3 – 30 • Potassium-Argon Dating Question 3 - 40 • When carbon-14 is left in an organism, scientists measure this amount that is left to find absolute age. Is the carbon-14 the radioactive element or the new element formed? Answer 3 – 40 • radioactive Question 3 - 50 •Why is Radioactive dating is good for igneous rocks but not sedimentary rocks Answer 3 – 50 • Scientists can date particles but not layers in sedimentary rocks. • Scientists can only date solid rocks. Question 4 - 10 • a record of the life forms and geologic events in Earth’s history Answer 4 – 10 • geological time scale Question 4 - 20 • After Precambrian Time, basic units of the GTS are Answer 4 – 20 • eras and periods Question 4 - 30 • three long units of time from Precambrian Time to the present, Ex: The Paleozoic, Mesozoic, and Cenozoic Answer 4 – 30 • Eras Question 4 - 40 • Later, _________________________ determined absolute age of divisions in the GTS Answer 4 – 40 • radioactive dating Question 4 - 50 • What happened during the Precambrian time period? Answer 4 – 50 • 1st oceans, atmospheres, landforms, and single-celled organisms. Question 5 - 10 • Scientists hypothesize that the Earth formed at the same time as other planets and the sun at what time? Answer 5 – 10 • about 4.6 billion years ago Question 5 - 20 • Earth started as a ball of Answer 5 – 20 • dust, rock, and ice in space Question 5 - 30 • As Earth cooled, water vapor condensed forming rain, accumulating to form Answer 5 – 30 • The oceans Question 5 - 40 • Without earth’s earliest life forms we would have no… Answer 5 – 40 • Oxygen/ozone Question 5 - 50 • How did the earth take shape? Answer 5 – 50 • Gravity pulled the mass together and thermal energy heated up the earth.