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science unit 2 lesson4
Terms in this set (90)
What is geology?
Geology is the scientific study of the origin, history, and structure and the processes that shape it.
What is Catastrophism?
Catastrophism is the principle that states that all geologic changes occur suddenly.
What is Uniformitarianism?
Uniformitarianism is the idea that the same geologic processes that shape Earth today have been at work throughout Earth's history.
What is catastrophic change in the Earth?
Catastrophically is that modern geologists recognize that catastrophes do cause some geologic change.
What is gradual change in the Earth?
Gradual change in the Earth is realized by geologists that neither uniformitarianism nor catastrophism accounts for all geologic change.
What is geologic time scale?
Geologic time scale divides Earth's into intervals of time defined by major events or changes on Earth.
How do you divide the Earth's long geologic history?
To divide the Earth's long geologic history, by using geologic time scale.
How do you mark major changes in the fossil record?
Major changes in the fossil records are marked by the movement of continents, lowering of global sea level, rapid climate change, and asteroid impacts are all thought to be causes.
What is Precambrian time?
Precambrian time begins with the formation of Earth about 4.6 billion years ago.
What is the Paleozoic Era?
The Paleozoic Era began about 540 million years ago as the global supercontinent pannotia was breaking up.
What is the Mesozoic Era?
The Mesozoic Era began about 250 million years ago after the permian mass extinction.
What is the Cenozoic Era?
The Cenozoic Era began about 65 million years ago with the cretaceous mass extinction and continues to the present.
What is Amber?
Amber is formed when hardened tree sap is buried and preserved in sediment.
How has Amber been very useful in scientific studies?
Amber has preserved some of the best insect fossils, such as ants, and spiders. Frogs and lizards have also been found in Amber.
Where do you find asphalt and what purpose does it serve?
There are places where asphalt wells up at the Earth's surface in thick, sticky pools. These asphalt pools have trapped and preserved many fossils over the past 40,000 years.
What happens when an organism dies?
When and organism dies, it often starts to decay or is eat by other organisms.
When and organism dies, what sometimes occurs?
Sometimes, however, organisms are quickly buried by sediment when they die. The sediment slows down the decay process and can protect parts of the body from damage. Hard parts of the organisms, such as shells and bones do not break down as easily as soft parts do.
What happens to the hard parts of dead organisms, when they have become buried in sediment and the sediment becomes rock?
When the sediments become rock, the hard parts of animals are preserved and become part of the rock as the sediments harden.
What happens in very cold places where the ground stays frozen all the time?
In very cold places on Earth, the soil can be frozen all the time. An animal that dies there can also be frozen. It is frozen with skin and flesh as well as bones. Because the cold temperatures slow down decay, many types of frozen fossils are preserved from the last ice age
What is petrification?
Petrification happens when an organism's tissues are replaced by minerals.
What are trace fossils?
A trace fossil is a fossilized structure that formed in sedimentary rock by animal activity on or in soft sediment.
What are some types of trace fossils?
Tracks are one type of trace fossils are animal activity on soft sediment that later became hard rock. Other types of trace fossils are burrows, pathways or shelter made by animals such as clams on the sea floor or rodents on land that dig in sediment. Some animal dung is considered a trace fossil.
What is the fossil record?
The fossil record is all of the fossils that have been collected on Earth. It is only part of the history because some things are still unknown. Not all the organisms that ever lived have left behind fossils. Also, there are many fossils that have not been discovered yet. The fossils that have been discovered provide important information about Earth's history.
What do fossils tell scientists?
Fossils can tell scientists about environmental changes over time. The types of fossils preserved in sedimentary rock show what the environment was like when the organisms were alive.
What do palm fronds tell scientists?
Palm fronds tell scientists that a tropical environment was present.
What type of fossils did scientists find in Antarctica and what did they mean?
Scientists found fossils of trees and dinosaurs in Antarctica. This means there must have been a warm climate in the past.
What can fossils tell scientists about life forms?
Fossils can tell scientists how life forms have changed over time. Major changes in Earth's environmental conditions and surface can influence an organism's survival and the types of adaptations that a species must have to survive.
Why do scientists study differences between different fossils and and between fossils and living organisms?
Scientists study differences between different fossils and fossils and living organisms to learn about life on Earth has changed.
How do rock and mineral fragments move from one place to another?
Rocks and mineral fragments move from one place to another when erosion occurs.
How is a natural cement formed?
A natural cement is formed when sediment is deposited in layers. As new layers of sediment are deposited, they cover old layers. The old layers become compacted. Dissolved minerals such as calcite and quartz, separate from water that passes through the sediment. This forms a natural cement that holds the rock and mineral fragments together in sedimentary rock.
How do scientists classify sedimentary rock?
Scientists use different characteristics to classify sedimentary rock. These provide evidence of the environment that the sedimentary rock formed in.
What does the texture of sedimentary rock show?
The texture of sedimentary rock shows the environment which the sediment was carried and deposited.
How is sedimentary rock arranged?
Sedimentary rock is arranged in layers.
How can sedimentary rock layers differ?
Sedimentary rock layers can differ from one another depending on the kind, size and color of their sediment.
What causes ripple marks on sedimentary rock?
Ripple marks on sedimentary rock record the motion wind or water waves over sediment.
What causes mud cracks on sedimentary rock?
Mud cracks form when fine-grained sediments at the bottom of a shallow body of water are exposed to the air and dry out. Mud cracks show that an ancient lake, stream, or ocean shoreline was once a part of an area.
Does the Earth's surface change? Why?
The Earth's surface is always changing. Continents change position continuously as tectonic plates move across Earth's surface.
What was Pangaea?
At one time the continents formed a single landmass, this was called Pangaea.
What happened to Pangaea?
About 200 million years ago, Pangaea broke apart. Since then, the continents have been slowly moving to their present locations, and continue to move today.
What shows scientists that Pangaea existed?
Evidence of Pangaea can be seen by the way rock types, mountains, and fossils are now distributed on Earth's surface.
How are mountain belts believed to be formed?
Scientists believe mountain-building events from tectonic plate movements produced different mountain belts on Earth.
What happens when continental plates collide?
When continental plates collide, mountain ranges can form. As they pull apart, magma can be released in volcanic eruptions. When they grind past one another, breaks in Earth's surface form, where earthquakes can occur
What is another way volcanoes and mountain can form?
Collisions between oceanic and continental plates can also cause volcanoes and the formation of mountains.
What is climate?
The climate of an area describes the weather conditions in the area over a long period of time.
How is climate determined?
Climate is mostly determined by temperature and precipitation. In addition to using fossils, scientists also analyze other materials to study how Earth's climate and environmental conditions have changed over time.
How is the age of a tree determined?
When most trees grow, a new layer of wood is added to the trunk every years. This forms rings around the circumference of the tree. Theses rings tell the age of the tree.
What else can scientists tell about a tree by the rings besides their age?
Scientists can use the tree rings to find out the climate during the life of a tree. If a tree ring is thick, it means the tree grew well-there was plenty of rain and favorable temperatures existed at the time. Thin tree rings mean the growing conditions were poor.
How do scientists use sediment removed from deep beneath the ocean floor?
Scientists remove cylinders of sediment from deep beneath the ocean floor. Preserved in these sediments are fossil remains of microscopic organisms that have died and settled on the ocean floor. These remains build up in layers, over time. If certain organisms are present, it can mean that the climate was particularly cold or warm at a certain time.
What can the chemical compositions of sediments from the ocean floor tell scientists?
The chemical composition of sediments, especially of the shells of certain microorganisms, can also be important. It shows what the composition was of the ocean water and atmosphere when the organisms were alive.
What are icecaps?
Icecaps are found in places such as Iceland and islands in the Arctic. The icecaps formed as older snow was squeezed into ice by new snow falling on top of it.
What is an ice core?
An ice core is a long cylinder of ice that scientists have drilled down and removed from and icecap.
What can ice cores tell scientists?
Ice cores give a history of Earth's climate over time. Some ice cores have regular layers called bands, which form each year. Band size shows how much precipitation fell during a given time. The composition of water and concentration of gases in the ice core show the conditions of the atmosphere at the time that the ice formed.
What is scientist's goal, when studying the Earth?
Scientist's goal studying the Earth is to find out the order in which events happened during Earth's history.
What is relative dating?
Relative dating is determining whether an object or event is older or younger than other objects or events.
How do scientists determine the order in which rock layers formed?
Using different pieces of information, scientists can find the order in which rock layers formed. Once they know the order, a relative age can be determined for each rock layer.
What causes sediment to be deposited in layers that are horizontal?
Scientists know that gravity causes sediment to be deposited in layers that are horizontal. Over time, different layers of sediment pile up on Earth's surface.
When rock layers pile up, which layers are on top, the younger or older layers?
As sediment piles up in layers, younger layers pile on top of older ones. As you go from top to bottom, the layers get older.
What is the law of superposition?
The law of superposition is the principle that states that younger rocks lie above older rocks if the layers have not been disturbed.
Why would rock layers not be horizontal?
If rock layers are not horizontal, something has disturbed them after they were formed.
What are some ways rock layers have been disturbed and are no longer horizontal?
Rock layers can be disturbed by tilting. Tilting happens when Earth's forces move rock layers up or down unevenly. The layers become slanted. Folding is the bending of rocks that can happen when rock layers are squeezed together. The bending is from stress on the rock. Folding can cause rock layers to be ruined over by so much that older layers end up on top of younger layers.
What is a fault in the Earth's surface?
A fault is a break or crack in Earth's crust where rocks can move.
What is an intrusion in the Earth's surface?
An intrusion is igneous rock that forms when magma is injected into rock and then cools and becomes hard.
What makes finding out the relative ages of rock layers difficult?
Folding, tilting, faults and intrusions can make finding out the relative ages of rock layers difficult. This can be even more complicated when a layer of rock is missing. Scientists call this missing layer of rock an unconformity.
What is an unconformity and how does it affect the geologic record?
An unconformity is a break in the geologic record that is made when rock layers are eroded or when sediment is not deposited for a long period of time. When scientists find an unconformity, they must question if the "missing layer" was simply never present or if it was removed.
What is the law of crosscutting relationships?
The law of crosscutting relationships states that a fault or a body of rock, such as an intrusion, must be younger than any feature or layer of rock that the fault or rock body cuts through.
What has to happen before a fault occurs in igneous rock?
If a fault has broken through igneous rock, the igneous rock must have been in place, and cool, before it could have been broken. The same is true for an unconformity.
How are fossils used to determine relative ages of rocks?
Fossils are the races or remains of an organism that lived long ago, most commonly preserved in sedimentary rock. Fossil forms of plants and animals show change over time, as they evolve. Scientists can classify fossilized organisms based on these changes. Then they can use that classification of fossils to find the relative ages of the rocks in which the fossils are found. Rock that contains fossils of organisms similar to those that live today is most likely younger than rock that contains fossils of ancient organisms.
What is a geologic column?
A geologic column is an ordered arrangement of rock layers that is based on the relative ages of the rocks, with the oldest rocks at the bottom of the column. It is made by piecing together different rock sequences from different areas. A geologic column represents and ideal image of a rock layer sequence that doesn't actually exist in any one place on Earth.
What happens when a scientist compares a rock layer with a similar layer in a geologic column that has the same fossils or that has the same relative position?
Scientists can compare a rock layer with a similar layer in a geologic column that has the same fossils or that has the same relative position. If the two layers match, then they probably formed around the same time.
What is absolute dating?
Absolute dating is determining the actual age of an event or object in years.
What is one way scientists determine absolute dating of rock and other materials?
One way scientists determine absolute dating or actual age of rock and other materials is by using radioactive isotopes.
What are isotopes?
Atoms of the same element that have a different number of neutrons are called isotopes. Many isotopes are stable, meaning they stay in their original form. But some isotopes are unstable, and break down to form different isotopes. The unstable isotopes are called radioactive.
What is radioactive decay?
The breakdown of a radioactive isotope into a stable isotope of the same element or of another element is called radioactive decay.
When does radioactive decay occur?
Radioactive decay for many isotopes happens when a neutron is converted to a proton, with the release of an electron
What is a parent isotope? A daughter isotope?
A parent isotope is a is a radioactie isotope. The stable isotope formed by its breakdown is call the daughter isotope.
How do some radioactive isotopes in mineral crystals act and what can they do?
Some radioactive isotopes in mineral crystals can act as clocks. These mineral crystals record the ages of the rocks in which the minerals formed. Scientists study the amounts of parent and daughter isotopes to date samples. If you know how fast a radioactive isotope decays, you can figure out the sample's absolute age.
What is radiometric dating?
Radiometric dating is finding the absolute age of a sample by detraining the relative percentages of a radioactive parent isotope and a stable daughter isotope .
What is the best rock for radiometric dating?
Igneous rock is often the best type of rock sample to use for radiometric dating. When igneous rock forms, elements are separated into different minerals in the rock. When they form, minerals in igneous rocks often contain only a parent isotope and none of the daughter isotope. This makes the isotope percentages easier to interpret and helps dating to be more accurate.
What are some radiometric dating methods?
Scientists use many different isotopes for radiometric dating. The half-life of an isotope is very important in determining the time rage that it is useful for dating. If the half-life is too short compared with at the age of the sample, there will be too little parent isotope left to measure. If the half-life is too long, there will not be enough daughter isotope to measure. Also, different methods may only be useful for certain types of materials.
What is radiocarbon dating?
The ages of wood, bones, shells, and other organic remains can be found by radiocarbon dating.
What is Potassium-Argon Dating?
Potassium-Argon Dating is often used to date igneous volcanic rocks. This method is used to date rocks that are between about 100,000 years and a few billion years old.
What is Uranium-Lead Dating?
Uranium-Lead Dating can be used to determine the age of igneous rocks that are between 100 million years and billions of years old. Uranium-Lead Dating was used to find the earliest accurate age of Earth.
How is radiometric dating used to determine the age of Earth?
Radiometric dating can be used to find the age of the Earth, but not by dating Earth rocks. The first rocks that formed on Earth have long ago been eroded or melted, or buried under younger rocks.
What is a meteorite?
Meteorites are small, rocky bodies that have traveled through space and fallen to Earth's surface. Scientists have found meteorites on Earth. Rocks from the moon have also been collected. Radiometric dating has been done on these rocks from other parts of our solar system.
What is the absolute ages of the rocks collected from our solar system?
The absolute ages of these samples show that our solar system, including Earth, is about 4.6 billion years old.
How can fossils help to determine the age of sedimentary rock?
By dating igneous rock layers above and below these fossil layers, scientists can determine the time span in which the organisms lived.
What are index fossils used for?
Index fossils, are fossils that are used to estimate the absolute age of the rock layers in which they are found. Once the absolute age of an index fossil is known, it can be used to determine the age of rock layers that contain the same index fossil anywhere on Earth.
What are the characteristics of an index fossil?
To be an index fossil, the organism from which the fossil formed must have lived during a relatively short geologic time span. The fossils of the organism must be relatively common and must be found over a large area. Index fossils must also have features that make them different from other fossils.
How are index fossils used?
Index fossils act as markers for the time that the organisms lived on Earth. Organisms that formed index fossils lived during short periods of geologic time. So, the rock layer that an index fossil is found in can be dated accurately.
What is another way to use index fossils?
Index fossils can also be used to date rock layers in separate areas. the appearance of the same index fossil in rock of different areas shows that the rock layers formed at about the same time.
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