More questions because brainscape sucks Flashcards
Has our atmosphere always had the same composition? If not, what processes have caused its
composition to change?
No, it has not. After loss of the hydrogen, helium and other hydrogen-containing gases from early Earth due to the Sun’s radiation, primitive Earth was devoid of an atmosphere. The first atmosphere was formed by outgassing of gases trapped in the interior of the early Earth, which still goes on today in volcanoes. The primary source of carbon/CO2 is outgassing from the Earth’s interior at midocean ridges, hotspot volcanoes, and subduction-related volcanic arcs.
Photosynthetic life reduced the carbon dioxide content of the atmosphere, it also started to produce oxygen. It was not until probably only 1 billion years ago that the reservoirs of oxidizable rock (banded rock) became saturated and the free oxygen stayed in the air.
- escape velocity
- solar radiation and wind
- greenhouse effect
Why does the Earth have an atmosphere, but the Moon does not?
There are three reasons why the moon has no atmosphere. The primary reason is because the moon is too small. Compared to the Earth, the moon is small bodied and thus cooled rapidly ending tectonic activity. This reduces the amount of gravity on the moon. Strong gravity is needed to hold an atmosphere into place. With weak gravity, gases that are emitted from the surface quickly are lost to outer space. Another reason is because the moon does not currently experience plate tectonics. Plate tectonics allows for a recycling of crust and convergence and divergence of plates occurs and this leads to volcanoes and gases escaping at the boundaries.
Another reason is because the moon is relatively close to the sun. This reason is tied closely to the moon having weak gravity. The solar wind from the sun helps strip away a weak atmosphere
How do the speeds of gas molecules in the atmosphere depend on the temperature?
At higher temperatures, molecules move faster. At a given temperature, bigger molecules move slower. (as temp increases, speed increases)
Which are moving faster in Earth’s atmosphere: hydrogen molecules or oxygen molecules?
Hydrogen
Why is there so little hydrogen and helium in Earth’s atmosphere?
The earth’s gravity is too low to retain hydrogen and helium and most escaped a long time ago. Hydrogen and helium are the first molecules to be lost.
They are small and light so they move very fast-their speeds are greater than the escape velocity from the earth.
Why can the Earth hold on to nitrogen and oxygen molecules
Nitrogen and oxygen are heavier molecules and therefore move slower and the gravity retains them in the atmosphere.
What two things define a mineral?
Minerals have a specific composition and specific crystal structure.
What is plate tectonics?
Depending on how the plates interact:
- transform boundaries are where 2 plates slide __ past each other.
- convergent boundaries are where 2 plates __, with one plate __ under the other.
- divergent boundaries are where 2 plates are moving __ away from each other. (new crustal rock is created at the junction, within continents they form __ __, and within oceanic plates they form __-__ ridges.)
Plate tectonics is the theory that the rigid crustal plates slide very slowly on the viscous mantle. If the plates move, we predict that at plate boundaries: earthquakes, volcanos, crust sinking/new crust forming.
-the earth’s crust is broken into 16 tectonic plates.
-explains changes in climate on continents
laterally
collide, subducting
away , rift valleys, mid ocean ridges
How does the age of the sea floor compare to the age of the continental crust and how does this support the theory of plate tectonics?
The age of the sea floor is younger compared to the age of the continental crust. The young age of the sea floor is caused by seafloor spreading in which molten material from the mantel rises through mid ocean ridges (along plate boundaries) and spreads the older material outwards on either side. This process moves the plates apart or together.
What are consequences of plate tectonics? What do we see concentrated along plate boundaries?
Volcanos, earthquakes, mountain ranges, creation of new sea floor.
Where a trench happens to run along the edge of a continent and subducting seafloor dives under the land, the marginal terrain will rise. The two plates, pressing, will create mountains, and volcanoes will appear as well.
How does plate tectonics affect the carbon cycle on Earth?
Why do plate tectonics make it
difficult to find old rock on Earth?
Convergent boundaries affect the carbon cycle in two ways: through subduction and eruption.
Subduction is the process by which continental crust slides beneath another portion of crust. The subducting crust melts and becomes magma, the material that fuels volcanic eruption. The melted crust contains carbon in the sediments and soils, thus recycling it through the mantle of the earth.
The melted crust convecting through the mantle will eventually resurface in the form of lava during eruptions from volcanoes. These volcanoes were originally formed by tectonic forces–where there is an excess of magma below the crust due to subduction, it is forced to erupt. The process of eruption includes degassing. Degassing is where carbon dioxide is released into the atmosphere as the eruption occurs because the dissolved carbon in the magma is unstable and under pressure, and is therefore forced to leave the fluid.
The recycling process can be seen in the diagram below. The trenches are the areas of subduction where a “slab” of crust is pulled into the earth. This crust, containing carbon, is then recycled through the mantle and later released through a ridge, either convergent or divergent.
old rocks are eroded and co2 rich sediments are washed into the ocean. they turn into carbonate rocks when reacting with calcium and subduct into the mantle and melt and are then outcast by volcanos.
What kind of information can we learn from paleomagnetism?
The earth’s magnetic field has reversed itself a number of hundreds of times, switching from north to south, south to north, at intervals that have varied in length.
What is shale made out of?
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles)
What is limestone made out of?
Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3). It often has variable amounts of silica in it, as well as varying amounts of clay, silt, and sand.
What is sandstone made out of?
Sandstone is a sedimentary rock. The sediment particles are clasts, or pieces, of minerals and fragments of rock, thus sandstone is a clastic sedimentary rock. It is composed mostly of sand particles, which are of a medium size; therefore, sandstone is a medium-grained clastic sedimentary rock.
What is one way to tell if a rock is relatively iron-rich or relatively silicon-rich?
Iron rich; darker in color: darker in color (grey, black)
silicon rich; lighter in color (white, light grey, pink, purple)
What is the technical name for a fine-grained igneous rock that cooled quickly?
extrusive=tiny crystals
What is the technical name for a coarse-grained igneous rock that cooled slowly?
intrusive=big crystals
Where is most of the carbon on Earth stored?
rocks and sediments (inaccessible)
Are all geological periods (e.g., Cambrian, Silurian, Triassic, etc) present in rock strata
everywhere? If not, why not?
No geological record is complete. If the area is not under water or being repaved by igneous activity, erosion is the dominant activity not creation.
Which kinds of rocks do we find on Earth?
Which of the three kinds of rocks makes up the
bedrock in Ohio?
Sedimentary: rocks are made out of sand, silt, or organic remains compressed in ocean and lake beds.
Igneous: rocks are cooled molten rocks
metamorphic: transformed by high pressure and heat. (tell us what rock used to be there: can’t get marble without limestone and can’t get slate without shale)
sedimentary rocks
What are the three major kinds of rocks and where do they actually come from?
igneous rocks are volcanic and form from molten material. They include not only lava spewed from volcanoes, but also rocks like granite, which are formed by magma that solidifies far underground.granite makes up large parts of all the continents. The seafloor is formed of a dark lava called basalt, the most common volcanic rock.
Sedimentary rocks are formed from eroded fragments of other rocks or even from the remains of plants or animals. The fragments accumulate in low-lying areas—lakes, oceans, and deserts—and then are compressed back into rock by the weight of overlying materials. Sandstone is formed from sand, mudstone from mud, and limestone from seashells, diatoms, or bonelike minerals precipitating out of calcium-rich water.
Fossils are most frequently found in sedimentary rock, which comes in layers, called strata.
Metamorphic rocks are sedimentary or igneous rocks that have been transformed by pressure, heat, or the intrusion of fluids. The heat may come from nearby magma or hot water intruding via hot springs. It can also come from subduction, when tectonic forces draw rocks deep beneath the Earth’s surface. Marble is metamorphosed limestone. Slate is metamorphosed shale.
What is the “faint sun paradox”?
Stars become more luminous as they age.
- increasing % of He in cores leads to an equilibrium with hotter core temps.
- sun about 30% less luminous just after birth
- our sun is now 40% more luminous than it was when the solar system 1st formed, temp of earth was also lower in the past.
What is snowball Earth?
How is it different than the faint sun paradox?
Snowball earth is when very long, deep, ice ages have occurred that caused the oceans to freeze.
It is caused by the amount of co2 in the atmosphere dropping and the green house effect decreasing-leading to colder temperatures. The polar ice caps also grow, which increases the amount of sunlight.
-2 episodes: later Proterozoic, early Proterozoic.
-caused by decrease in co2 (during period with rise in oxygen) in atmosphere whereas faint sun paradox is caused by increasing % of helium in the core.
