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Geologic Time (Ch 8)

Name:________________________
Class: ___________ Date: ________
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Across
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Preserved remains can be found in ______, which is the substance made from hardened tree resin.
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Earth early atmosphere may have included light gases such as _______ and helium.
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Preserved _____ are found when entire organisms are preserved.
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During _____ decay, the atoms of one element break down to form atoms of another element.
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Scientist have determined that Earth is about 4.6 _______ years old.
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______ is the change in living things over time.
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The ______ age is the number of years that have passed since the rock formed.
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Geologist use the law of _____ to determine the relative ages of sedimentary rock layers.
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______-14 is used to date fossils.
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The geologic time _____ is a record of the geologic events and the evolution of life forms as shown in the fossil record.
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Organisms could live on land after the _____ layer formed, that blocked the ultraviolet rays of the sun.
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Scientists who study fossils are called _______.
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Scientist use the rate at which radioactive elements _____ to calculate the age of rock.
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A/An ______ is a unit of time that subdivides eras.
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A carbon ______, is type of fossil that is a extremely thin layer of carbon on a rock.
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When the Earth was forming, denser materials sank toward the center, forming Earth's dense iron _____.
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At the beginning of the _____ Era, a great number of different kinds of organisms evolved. For the first time, many organisms had hard parts including shells and outer skeletons.
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A fossilized _____ is one example of a trace fossil.
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The earliest known life forms on Earth were ____ cells organisms.
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A _____ is a ball of dust, gas and ice that orbits the sun.
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A type of organism is _____ if it no longer exists and will never live again on Earth.
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The ______ age of a rock is its age compared to the ages of other rocks.
Down
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A ____ is a break in the Earth's crust.
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A/An _____ is a long unit of time used to divide the time between Precambrian time and the present.
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Preserved remains or traces of living things.
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A _____ is a hollow area in sediment in the shape of an organism or part of an organism.
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A ____ is a solid copy of the shape of an organism.
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During the _____ Era, mammals evolved to live in many different environments - on land, in water, and even in the air.
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Many early animals were _____ or animals without backbones.
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Scientist hypothesize that a ____ extinction occurred when an asteroid from space struck Earth at the close of the Cretaceous Period.
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Reptiles were so successful during the _____ Era that this time is often called the Age of Reptiles.
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An ____ fossil is a fossil that is widely distributed and represents an organism that existed for a geologically short period.
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A/An ____ is an animal that lives part of its life on land and part of its life in water.
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In undisturbed horizontal sedimentary rock layers, the oldest layer is at the ______.
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An _____ is a gap in the geological record where rock layers have been lost due to erosion.
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______ have scaly skin and lay eggs that have tough leathery shells.
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The earliest part of the geologic time scale was named _____ time.
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Lava that hardens on the surface and forms igneous rock is called an _____.
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Magma that cools and hardens below the surface is an _____.
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_____ fossils are fossils in which minerals replace all or part of an organism.
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The _____ of a radioactive element is the time it takes for half of the radioactive atoms to decay.
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A fault is always _____ than the rock it cuts through.
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_____ fossils provide evidence of the activities of ancient organisms.
Welcome to Mrs Palumbo Science Puzzle on Geologic Time.