Earths Resources Midterm

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Columbia University *

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72448

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Geography

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Oct 30, 2023

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1. Reserves vs Resources & General Questions Under what circumstances does the quantity of reserves of a given commodity increase? decrease? The quantity of a reserve can increase if there is a new discovery or technological advancements, and it decreases when it is mined out. What are renewable and non-renewable resources? List three of each. Renewable resources are those materials that are replenished on short timescales of a few months or years. These include the organic materials from plants and animals, aswell as the energy we draw from wind, flowing water, and the sun’s heat. Non-renewable resources are those materials of which Earth contains a fixed quantity and which are not replenished by natural processes operating on short timescales. These include oil, natural gas, coal, copper, and other mineral products we dig and pump from Earth. When the price of a mineral commodity of fossil fuel rises, what happens to the reserves? The reserves increase when the price (market value) of a fossil fuel increases because more will be economic to extract. Define in simple terms the diffference between a reserve and a resource? A resource is the concentration of naturally occurring solid, liquid, or gaseous material, in or on Earth’s crust, in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible. A reserve is the part of the resources that can be economically and legally extracted at a given time. The resource must meet economic, legal, and environmental constraints. Explain how market prices have an impact on the quantitiy of reserves for a given mineral or commodity? The quantity of a reserve increases as the market value of a mineral/commodity rises, and decreases as the market value falls. How do commodity resources become reserves? Give two examples. Resources can become reserves when there is a technological advancement that allows for economic extraction. For example this occurred when a new bulk mining process in the beginning of the 20th century allowed for copper deposits to become reserves. Another example of this is after WWII, when iron reserves were running low, a new mining technology allowed for “taconites” to be worked with and they now supply much of the iron in the US. What is a mineral or commodity reserve?

A reserve is the part of the resources that can be economically and legally extracted at a given time. The resource must meet economic, legal, and environmental constraints. What is a mineral or commodity resource? A resource is the concentration of naturally occurring solid, liquid, or gaseous material, in or on Earth’s crust, in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible. What is one watt equivalent to? A watt is equivalent to work done at a rate of one joule per second (1 J/ 1 sec). What constraints influence whether or not a resource is a reserve? Constraints include economic, environmental, and legal boundaries. This includes land ownership, the presence of endangered animals or plants, potential carcinogenic effects of mining, and more on top of the economic factor. What is the doubling time for commodity consumption growing at 3% per year? Doubling time is calculated as the natural log of 2 divided by the rate of growth. Thus for doubling time it is 0.7/rate for the time. For a growth rate of 3% or 0.03, the doubling time is 0.7/0.03 which is about 23 years. What is the time recquired for a factor of 10 increase in commodity consumption growing at 3% per year? Doubling time is calculated as the natural log of 10 divided by the rate of growth. Thus for a factor of 10 increase it is 2.3/rate for the time. For a growth rate of 3% or 0.03, the factor of 10 increase of time is 2.3/0.03 which is about 77 years. What are the units of reserve to production ratio? The reserves to production ratio is the reserves available (eg Gt) divided by the rate of production (eg Gt/yr). Thus the unit is time, and the time that is calculated is the time the commodity would run out if no new reserves are proven and if production continues at a constant rate. 2. Environmental Impacts of Resource Use Acid rain is considered one of the most serious forms of pollution. What causes it? When sulfur-bearing minerals in coal are burned, sulfur oxides are released which combine with water vapor in the atmosphere to form sulfuric acid. Nitrogen oxides, which react with water vapor to form nitric acid, are created from high temperature combustion (like in the burning of

fossil fuels) in atmospheres with high levels of nitrogen. These two acids in the atmosphere become part of the rainfall, and as acids, lower the pH. List two environmental impacts due to use of coal in power generation and manufacturing? What are two main methods of coal mining? Which is safer for those involved in producing coal? One environmental impact from the use of coal in power generation is acid rain, which results from the sulfur oxides that arise when coal is burned, which turn into sulfuric acid in the rainfall. Another environmental impact from coal is that strip mining for coal leaves mounds of waste material that have no vegetation and are too steep to farm, thus devastating large plots of land. Another impact of coal is when burned it contributes to the greenhouse effect, by increasing carbon dioxide in our atmosphere. A final impact of coal use in power generation is that when burned trace amounts of Mercury are released, and coal combustion is the world’s greatest source of Mercury pollution. The two main methods of coal mining are underground mining and surface mining. Surface mining is safer for those involved in producing coal. What is one acid in acid rain? The acids in acid rain are sulfuric and nitric acid. What is the difference between external and internal costs of resource use and pollution? Internal costs are costs taken on by the producer for the resource use and pollution they take part in. External costs are costs taken on by the public for the resource use and pollution of a producer. What are two examples of the change from external to internal costs? An example of internalizing an external cost would be for example mandating companies to offset their carbon emissions. This changes the external cost, climate change for everyone, to an internal cost, a fee for the company. Another example is in early London where people chucked human waste into the streets. Everyone bore the cost of this through the smell. The government interalized this external cost by making people pay a tax for create a central sewer system. Instead of making other people pay with the smell, the people creating waste had to pay. How have US government regulations on Mercury emissions affected the rate of replacement versus renovation of older coal fired power plants in the US? The US government made regulations that all new coal fired power plants could not emit any Mercuryt, but this left the loophole of the old power plants being fine to emit Mercury. Thus, people just renovated old coal power plants instead of repalcing them or making new ones.

In the United States, what method is used to mine most of the coal in the High Plains Rocky Mountain region? In general is the coal in this region higher or lower grade than the coal obtained from the Appalachians in the previou century? Strip mining is used to mine most of the coal in the High Plains Rocky Mountain region. In general the coal in this region is lower grade than the Appalachian coal, the area is richest in sub-bituminous coal where as the Appalachian coal is bituminous. What is pH? It is a measure of hydrogen ions. It is the -log10 of H+ ion concentration in moles per liter. In acid rain, is the pH higher or lower than normal? The pH is lower than normal, since the rain is more acidic. What is the largest source of human Mercury emissions to the atmosphere? The largest source of Mercury emissions to the atmosphere is from coal combustion in power plants, as it releases trace amounts of Mercury. 3. Plate Tectonics & Composition of the Earth Around which ocean basin (Artic, Atlantic, Indian, Pacific…), are most sub-aerial volcanoes found? Why is there volcanism in this relatively cool setting? Most volcanoes are found along a belt called the “Ring of Fire” that encircles the Pacific Ocean. In the context of crystallization of magmas, what are incompatible elements? As magma crystallizes, the incompatible elements are those that don’t fit easily into the crystal structures of minerals (because of size or charge) and thus stay preferentially in the liquid phase. Is continental crust thicker or thinner than oceanic crust? The continental crust is thicker than the ocean crust. Is oceanic crust denser or less dense than continental crust? Oceanic crust is more dense than continental crust. Name four of the twelve most abundant elements on Earth. Some of the most abundant elements on earth include oxygen, silicon, aluminum, and iron. What are two natural sources of thermal energy (heat) on Earth? The heat from the Sun and the heat in the Earth’s interior which is given off by the natural decay of radioactive elements.

What kind of plate boundary forms the mid-ocean ridges? What is the heat source for submarine hydrothermal vents along the mid-ocean ridges? Divergent plate boundaries, or spreading zones, form the mid-ocean ridges, which are where new magma is brought upward. The heat source for these submarine hydrothermal vents is from the heat given off by the natural decay of radioactive elements in the Earth’s interior (like uranium and potassium) which is then dissipated and carried upward through large convection cells in the mantle, where a lot of the heat is released at these mid-oceanic ridges. What property of the Earth’s magnetic field was crucial in the discovery of seafloor spreading. Draw a schematic “map” illustrating a spreading center and the remnant magnetizzation recorded by the surrounding sea floor. Seemingly random reversals in the polarity of the Earth’s magnetic field were crucial in the disovery of seafloor spreading. Magma particles point towards one pole or the other, and then “freeze” into place during cooling. The stripes of magma particles facing different ways were indicative of a reversal of polarity. The reason they were crucial is because scientists reading magnetization maps realized that these stripes were symmetrical along lines, which they determiend to be spreading centers, and they were able to figure out that the seafloor was spreading at these points. When they are molten, which are hotter, mafic magmas or felsic magmas? Which have more Mg and Fe, mafic igneous rocks or felsic igneous rocks? Which have more Al, Si, Na, and K, mafic igneous rocks or felsic igneous rocks? Which have more “incompatible elements”, mafic igneous rocks or felsic igneous rocks? Which have more “compatible elements” mafic igneous rocks or felsic igneous rocks? In molten form, mafic magmas are hotter than felsic magmas. Mafic igneous rocks have more Mg and Fe and are rich in compatible elements. These make up the oceanic crust. Felsic igneous rocks have more Al, Si, Na, and K and are rich in incompatible elements. These make up the continental crust. Where would you expect to find igneous rocks with more SiO2, in oceanic crust or continental crust? You would expect to find igneous rocks with more SiO2 in continental crust, as this is what makes the continental crust so much less dense. Why is it unlikely to find coal deposits in igneous rocks? Igenous rocks form when magma cools and crystallizes, but coal is not derived from molten material. Coal is sedimentary rock, with vegetal origins.

With the exception of some small fragments thrust onto the continents, the oldest oceanic crust on Earth is less than 200 million years old. The Earth has had oceans and oceanic crust, for several billion years. Where did the older oceanic crust go? At subduction zones, oceanic crust slides under other tectonic plates and sinks back into the mantle. Below the surface layers affected by the weather and short term climate change, how does temperature vary with depth in the solid crust of the Earth? How does temperature vary with depth in large ocean basins? How does this affect the stability of gas hydrates? How does this affect potential methods for storage of CO2 captured frm exhaust gas at power plants? It gets hotter the deeper into the solid crust of the Earth. The opposite occurs in the oceans. As you go deeper in the ocean, temperature decreases and pressure increases. Gas hydrates are stable at high pressure and low temperatures, and thus are more stable deeper in the ocean. CO2 is more dense than water at temperatures less than 10 C and high pressures, so there is a potential to store CO2 in puddles on the seafloor. One type of meteorite carbonaceous chondreites is very helpful in estimating the bulk composition of the Earth. What are some similarities and differences between the composition of carbonaceous chondites and the composition of the solar atmosphere? Compared to the solar atmosphere, carbonaceous chondrites are depleted in elements that form gases at low temperature, thought to have been blown outward by the “solar wind” during condensation of the solar nebula What are black smokers and how do they form? Black smokers are vents on the seafloor from which hot hydrothermal fluids are issued. Upon entering the cold ocean waters, these fluids rapidly mix, cool, and precipitate very fine iron and other metal sulfides that appear as black smoke. These vents form near spreading centers when cold sea water percolates through the ocean crust, is heated by hot magma, and reemerges because of the pressure as hydrothermal fluids. What are the four main layers of the Earth's interior below the oceans and atmosphere, two composed mainly of silicates plus some metal-oxides and two composed mainly of metallic compounds? Which one is liquid? The four main layers consist of the inner core, solid iron, the outer core, liquid iron, the mantle, composed of Fe-Mg silicates, and the crust. What are the three main types of tectonic plate boundaries?

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