 | Term | Definition |
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geology |
the study of the structure of planet Earth and the forces that make and shape Earth |
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erosion |
the process by which water, ice, or wind breaks down rock |
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uniformitarianism |
the geologic principle that the same geologic processes that operate today operated in the past to change Earth's surface |
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igneous rock |
a type of rock that forms from the cooling of molten rock at or below the surface |
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sedimentary rock |
rock formed of hardened layers of sediments |
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metamorphic rock |
a type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions |
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rock cycle |
a series of processes on the surface and inside Earth that slowly change rocks from one kind to another |
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magma |
molten material beneath Earth's surface |
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lava |
liquid magma that reaches the surface |
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relative age |
the age of rock compared to the ages of rock layers |
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absolute age |
the age of a rock given as the number of years since the rock formed |
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law of superposition |
the geologic principle that states that in a horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it |
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extrusion |
an igneous rock layer formed when lava flows onto Earth's surface and hardens |
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intrusion |
an igneous rock layer formed when magma hardens beneath Earth's surface |
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fault |
a break or crack in Earth's crust along which the rocks move |
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unconformity |
a place where an old, eroded rock surface is in contact with a newer rock layer |
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inclusion |
a piece of rock that is contained in another rock; it is always younger than the rock containing it |
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index fossil |
fossils of widely distributed organisms that lived during only one short period |
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atoms |
the smallest particles of an element |
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element |
any substance that cannot be broken down into simpler substances |
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radioactive decay |
the breakdown of a radioactive element releasing particles and energy |
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half-life |
the time it takes for half of the atoms in a radioactive element to decay |
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plates |
one of the major pieces of Earth's rocky outer layer on which continents and oceans move |
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theory of plate tectonics |
theory that states that Earth's plates move slowly in different directions |
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continental drift |
the very slow motion of the continents |
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geologic time scale |
a record of the geologic events and life forms in Earth's history |
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eras |
one of the three long units of geologic time between the Precambrian and the present |
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periods |
one of the units of geologic time in which geologists divide eras |
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invertebrates |
an animal that does not have a backbone |
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vertebrate |
an animal that has a backbone |
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amphibian |
an animal that spends its early life in water and its adult life on land |
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reptiles |
an animal that lays eggs and has lungs and scaly skin |
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mass extinction |
when many types of living things become extinct at the same time |
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mammal |
an endothermic vertebrate with a four chambered heart, skin covered with fur or hair and young fed with milk from the mother's body |
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The principle of uniformitarianism states that... |
the geologic process that operate today also operated in the past. |
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Geologists classify rocks into what three groups? |
igneous, sedimentary, and metamorphic |
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Forces inside Earth and at the surface produce a rock cycle that... |
... builds, changes, and destroys rocks |
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According to the law of superposition, in horizontal sedimentary rock layers the oldest layer is where? |
it is at the bottom. |
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In horizontal sedimentary rock layers each higher layer is younger than the layer... |
below it. |
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To determine relative age what do geologists study? |
Thy study extrusions and intrusions of igneous rock, faults, gaps in the geologic record, and inclusions. |
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Why are index fossils useful? |
They are useful because they tell the relative age of rock layers in which they occur. |
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What happens during the process of radioactive decay? |
the atoms of one element break down to form atoms of another element. |
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What is radioactive dating used for? |
they are used to determine the absolute age of rocks. |
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What does radioactive dating show about moon rocks? |
It shows that the oldest moon rocks are 4.6 billion years old. |
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What can scientists infer from the moon rocks? |
From the moon rocks scientists infer that Earth is a little bit older meaning that Earth is roughly 4.6 billion years old. |
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According to the theory of plate tectonics... |
... Earth's landmasses have changed position over time because they are part of plates that are slowly moving. |
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As Earth's plates moved, landmasses changed their locations. These changes affected what? |
it affected where different kinds of organisms, past and present, are located. |
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Because he time span of Earth's past is so great, geologists use what to show Earth's history? |
they use the geologic time scale. |
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When did the firsts organisms live on Earth and what were they? |
3.5 million years ago and they were single-celled organisms that were similar to present-day bacteria. |
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What happened at the beginning of the Paleozoic Era? |
many different kinds of organisms evolved. |
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What were the first vertebrates? |
jawless fish |
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What happened during the Devonian Period? |
vertebrates began to invade the land |
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What did the mass extinction known as the Permian extinction affect? |
it affected both plants and animals on land and in the seas. |
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What happened during the Permian Period about 260 million years ago? |
Earth's continents moved together to form a great landmass or supercontinent called Pangea. |
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What was the Mesozoic Era also known as and why? |
Age of Reptiles because reptiles were so successful during the Mesozoic Era |
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At the end of the Cretaceous Period about 65 million years ago another mass extinction occurred . What do scientists hypothesize about the mass extinction? |
They hypothesize that an asteroid hit earth and created a large cloud that blocked the sun and killed out most animals. |
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What happened during the Cenozoic Era? |
mammals evolved to live in many different environments on land, in water, and even in air. |
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What happened to Earth's climate during the Quaternary Period? |
Earth's climate cooled causing a series of ice ages |
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What happens in the rock cycle? |
In the rock cycle igneous rock erodes into sediment which then goes through deposition and creates sedimentary rock which goes through heat and pressure which turns it into metamorphic rock which melts into magma and lava which goes through volcanic activity to form igneous rock once again |
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How are rocks classified? |
they are classified into the three groups of igneous sedimentary and metamorphic rock |
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How is radioactive dating used to figure out the absolute age of rocks? |
Scientists first measure the amount of radioactive element in a mineral in a rock. then they measure the amount of stable element into which the radioactive element decays. then they calculate the ratio of the radioactive element to the stable element, from that they can determine the age of the rock |
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How old is Earth according to radioactive dating? |
It is about 4.6 billion years old |
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Why have Earth's landmarks changed position over time? |
They have changed position over time because of because of the theory of plate tectonics |
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How did the changing face of the Earth affect the distribution of living things on Earth? |
It affected the distribution of living things on Earth because species got seperated when the continents seperated and ended up creating more species. |
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What are the oldest fossils on Earth and what are they most similar to? |
the oldest fossil is of single-celled organism and it is most similar to present-day bacteria. |
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Why do geologists use the geologic time scale? |
they use it to show Earth's history |
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What happened at the end of the Mesozoic Era about 65 million years ago? |
a mass extinction |
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When did mammals become well adapted to many environments? |
during the Cenozoic Era |
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During the beginning of the Paleozoic Era where did all animals live? |
They all lived in the ocean. |
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During the Ordovician and Silurian periods what animals did invertebrates have to share the sea with? |
they had to share it with vertebrates |
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During what period did plants evolve n land? |
the Silurian period |
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During what period did reptiles evolve on land? |
Carboniferous period |
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During what period did birds evolve? |
Jurassic |
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During what period did dinosaurs evolve? |
Jurassic |
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When did Homo Sapiens(humans) evolve? |
The Quaternary |
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During what period did very large birds and mammals evolve? |
Tertiary |
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When did the ice ages occur? |
Quaternary |
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