Earth science final sem 2 Flashcards
How are sedimentary rocks created
By deposition, burial, compaction, and cementation. Form in oceans or lake bottoms where most sediments are deposited
How are igneous rocks created?
Magma rising from the mantle. It forms above the surface (extrusive) or below the surface (intrusive)
How are metamorphic rocks created?
Converging plates, contact with magma aka contact metamorphism, found under mountain ranges( highly folded units) and found around the edges of igneous intrusions
What is the law of original horizontally?
All sedimentary rock layers and some extrusive igneous rocks are originally deposited in horizontal layers
What is the law of superposition?
In undisturbed rock, the layers on the bottom are older than the layers above
What is the law of disturbed rock strata
Any process which disturbs the rock must be younger than the rock it disturbs
What is the law of crosscutting?
Any feature that cuts across layers of rock must be younger than all the rock layers it cut across
What is tilting?
A type of disturbance that tilts rock layers and is caused by plate movement
What is folding?
A type of disturbance that folds rock layers and is caused by plate movements
What are the faults?
A fracture in the crust along with the lithosphere moves and is caused by plate movement
What are intrusions
Magma that cuts onto rock layers and cools below Earth’s surface forming igneous rock which is caused by rising magma
What is a dike?
Igneous rock intrudes along with fractures in existing rock (vertical/diagonal)
What is sill?
Igneous rock intrudes along with sedimentary layers (horizontal)
What is batholith?
A large mass of igneous rock with an irregular shape
What is inclusion?
Parent rock breaks off into magma and does not melt and is found in the cooled igneous rock
What is extrusion?
Molten rock that reaches Earth’s surface(lava) and cools forming igneous rocks and is caused by rising magma that reaches the surface
What is uplift?
A type of disturbance that raises up a large area of the Earth’s crust and is caused by plate movement
What is subsidence?
A type of disturbance that lowers a large area of Earth’s crust and is caused by plate movement of erosion
What is unconformity?
A gap in the rock record where layers have been eroded and new layers have been deposited on top
What are the steps to unconformity?
Deposition (This usually happens on the ocean floor below sea levels), Uplift (The sedimentary rock is lifted above sea level exposing it to erosion), Erosion and subsidence (Some of these layers are removed and the surface is lowered below sea level exposing it to deposition), and deposition (new layers are deposited where the missing rock was)
What are fossils?
Preserved remains of organisms in rocks, primarily sedimentary
What are index fossils?
Allow geologist to narrow the time of a rock unit to a specific time period
What are the characteristics of an index fossil?
Distinctive features/easily recognizable, Widespread/ all over the world, Abundant/There are a lot of them everywhere, Hard parts or shells/Easy to preserve, and Short-lived/Not around for a long time
What is absolute dating?
Quantitive (has an exact number), different than relative dating because it’s more exact
What are radioactive isotopes
Allows us to absolutely date rocks which are done by looking at the ratio of radioactive (parent) isotopes vs stable (daughter) elements
What is radioactive decay?
Unstable elements will become stable elements
What are half-lives?
The amount of time it takes for half of a sample to decay
What are the rules for radioactive dating
Heat, pressure and chemical composition don’t affect decay. Radioactive isotopes decay at a constant rate. Different isotopes have different rates of decay
What is an eclipse?
The blocking of light when one celestial body moves into the shadow of another celestial body
What is a solar eclipse?
When the moon is blocking the sunlight to the Earth (New moon)
What is a lunar eclipse?
When the Earth is blocking the moon from the sun (Full moon)
What is a total eclipse?
An eclipse in which the whole disc of the sun or moon is covered. Occurs within the umbra (full shadow)
What is the partial eclipse?
An eclipse in which part of the disc of the sun or moon is covered. Occurs within penumbra (partial shadow)
Why do eclipses not occur every month?
The moon’s orbit around the Earth is tilted 5 degrees compared to the Earth’s orbit around the sun
What are the different phases of the moon?
New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning crescent
What is waxing?
Moon phases when the illuminated portion grows. The right side is illuminated
What is waning?
Moon phases when illuminated portion shrinks. The left side is illuminated
Why does the same side of the moon always face the Earth?
The Moon’s period of rotation is the same as its period of revolution
What happens at apogee and perigee?
At apogee, the moon is farther and appears smaller. At perigee, the moon is closer and appears larger
What is an orbit?
The path of an object around the sun
What is the difference between perihelion and aphelion?
Perihelion points in orbit nearest to the sun. More gravitational attraction. Planets move faster in its orbit. Aphelion is the point in the orbit farthest from the sun. Less gravitational attraction. The planet moves slower in its orbit. Closer on Jan 3rd and farther on July 4th
What is an ellipse?
An oval, an elongated circle with two centers called foci.
What are foci and major axis?
Central points of an ellipse, the sun is always located at one of the foci and the major axis is the longest straight line distance across the eclipse. Passes through foci
What is eccentricity?
The degree or flatness or ovalness of an eclipse
