Oceanography - Exam 2
Discuss the formation of atolls. Who came up with the idea? When?
An Atoll is a circular ring of low-lying coral reef islands. Charles Darwin came up with this idea during his voyage of the Beagle from 1831 - 1836.
Be able to list ways that water is considered unique.
unique because of surface tension, its a strong covalent, weak hydrogen (each water molecule can establish hydrogen bonds), all three states, universal solvent, and holds heat and energy.
How does land elevation affect precipitation near the ocean?
Because the continents rise high above the sea surface, they affect the winds in another way. As the winds sweep across the ocean, they reach the land and are forced to rise as they encounter the land. The upward deflection cools the air (causing rain on the windward side of the islands and mountains). On the leeward side - there is a low precipitation zone.
Identify what biogenous, lithogenous and hydrogenous sediments are and where they are present on the seafloor.
Biogenous - sediments derived from organisms, these may include shell and coral fragments as well as the hard skeletal parts of single-celled phytoplankton and zooplankton that live in the surface waters. Most free-floating, some benthic. Lithogenous - from weathered and eroded rocks, Terrigenous (derived from land), Volcanogenic cosmogenics (from volcanoes). Mostly deposited on continental margin (Neritic) Hydrogenous - sediments derived from the water, produced in the water by chemical reactions. Most are formed by the slow precipitation of minerals onto the sea floor, but some are created by the precipitation of minerals in the water column in plumes of recirculated water at hydrothermal vents along ocean ridge system. Include some carbonates (limestone-type deposits), phosphorites (phosphorus in the form of phosphate in crusts and nodules), salts, and manganese nodules.
Why can fertilizing the ocean surface with Fe (iron) be used to drawdown CO2 from the atmosphere?
By fertilizing with iron, it can increased plankton blooms in ocean and draw 60 billion tons of carbon out of atmosphere.
Why are the carbon dioxide concentrations of the atmosphere changing? Why is there concern about these changes?
Carbon dioxide concentrations of the atmosphere are changing because of the effects of deforestation, burning of fossil fuels, and growth of human population. There is concern because it can increase global warming, increase sea levels, affect oceanic circulation and deplete ozone.
How is the CCD defined? What determines the depth that is occurs within the ocean?
Carbonate Compensation Depth (CCD) is the depth at which the amount of calcareous material preserved falls below 20% of the total sediment. CCD is the depth at which the rate of accumulation of calcium carbonate is equal to the rate at which it is dissolved.
Explain the global distribution of sediments on the seafloor in the world ocean.
Carbonate: shallow water - generally found in shallower regions of the world ocean. Silicious: cold water - Equatorial upwelling in the pacific and ice-edge processes in the Antarctic contribute to the productivity of diatoms and the accumulation of siliceous sediments. Terrigenous: near river deltas - dominates near the mouths of major rivers.
What record do icebergs leave on the seafloor? Explain why this iceberg rafting record is important information.
Carry large rocks out to sea and shows the patterns of movement. This can tell when glaciers were on land.
What are the 6 major ions in seawater. Why are they termed conservative constitutes? What does the principle of constant proportions mean? Explain how this concept was verified by the Challenger expedition.
Cations - Sodium (Na+), Magnesium (Mg2+), Calcium (Ca2+), and Potassium (K+) Anions - Chloride (CI-), and Sulfate (SO4-) Termed conservative constitutes because the ratios of the major constituents of seawater do not change with changes in total salt content and these are not generally removed or added by living organisms Constant of Proportions - states that regardless of variations in salinity, the ratio between the amounts of major ions in open-ocean water are constant. During the world cruise of the Challenger Expedition (1872-1876), 77 water samples were collected from different depths and locations. When chemist William Dittmar analyzed these samples, he verified Georg Forchhammer's findings (he found that several hundred seawater samples had constant proportions).
What is a turbidity current? Where would you expect a turbidity current to occur?
Fast-moving avalanches of mud, sand, and water that flow down the slope, eroding and picking up sediment as they gain speed. Caused by earthquakes or the overloading of sediments on steep slopes.
Identify three ions considered important in marine nutrients.
Fertilizers of the ocean: Nitrogen (N), Phosphorus (P), and Silicon (Si) - silica forms the hard outer wall of the single-celled diatoms and the skeletal parts of some protozoans.
Explain why ice floats. What happens to the arrangement of water molecules when ice freezes? The physical structure of ice is shown in class.
Ice expands when frozen and pockets of air get inside and make it lighter. Ice is like a crystal with a hole in the middle.
Explain how sea surface salinity is modified by evaporation, precipitation, and runoff from the continents. Why is the salinity of ocean surface water associated with latitude?
In major ocean basins, 3.5% of the weight of seawater is dissolved salt and 96.5% is water - the average ocean salinity is approximately 35%. Evaporation, precipitation, and runoff affect the amount of salt in seawater.
Why can sound be used to measure depth in the ocean (i.e. sonar or echo sounding) whereas light cannot.
Light cannot penetrate that deep but Sound waves can. Sound travels faster and farther in seawater.
List examples of seabed resources (manganese nodules, gas hydrates, phosphorite nodules, oil and gas). How and where do they form?
Manganese Nodules - found scattered across the world's deep ocean floors, with particular concentrations in the red clay regions of the northeastern pacific. The nodules grow very slowly, but they are present in huge quantities. Gas Hydrates - combination of natural gas, primarily methane and water which forms a solid, ice-like structure under pressure at low temperatures. Occur within ocean-floor sediments, especially in parts of the ocean that are cold and deeper than 500 m. Common settings are along passive margins and trenches. Also occur on land, beneath frozen arctic tundra. Phosphorite Nodules - found in shallow waters as phosphorite muds and sands containing 12% to 18% phosphate and as nodules on the continental shelf and slope. Known to exist off Florida, California, Mexico, Peru, Australia, Japan, and north western and southern Africa. Recently a substantial source of phosphorite was located in Onslow Bay, NC. Oil and Gas - Oil deposits are generally found at depths less than 3km, and below 7km only gas is found. Major offshore oil fields are found in the Gulf of Mexico, Persian Gulf, and the North Sea, and off the northern coast of Australia, southern coast of California, and the coasts of the Arctic Ocean.
Describe the difference between neritic and pelagic marine sediments.
Neritic sediments are found near the continental margins and islands and have a wide range of particle sizes. Most are eroded from rock on land and transported to the coast by rivers. Once in ocean, they are spread across the continental shelf and down the slope by eaves, currents, and turbidity currents. The largest particles are left near coastal beaches, whereas the smaller particles are transported farther from shore. Pelagic sediments are fine-grained and collect slowly on the deep-sea floor. The thickness of these sediments is related to the length of time they have been accumulating or the age of the sea floor they cover. Accumulation rates for pelagic sediments are much slower than those of typical neritic sediments.
The specific heat of water is higher than rock and soil. How does this affect the heat capacity of the oceans vs. air? How does this determine the annual temperature range of both land and the oceans?
Oceans have very high heat capacity due to the high specific heat of water. The seasonal temperature ranges at high latitudes are greater for land than for the oceans and the annual range of ocean surface temperatures is greatest at the middle latitudes. Because of the lack of land in the southern hemisphere, the oceans, with their high heat capacity, control the annual temperature range in southern middle latitudes (opposite in Northern Hemisphere).
Identify organisms that form calcareous and siliceous oozes. How does the CCD determine where you find them?
Organisms that form Calcareous oozes - group of phytoplankton called coccolithophorids (covered with calcareous plates called coccoliths), snails called pteropods, and amoeba-like animals called foraminifera. Calcareous ooze tends to accumulate on the seafloor at depths above the CCD and is generally absent at depths below the CCD. Organisms that form Siliceous oozes - group of phytoplankton called diatoms (found at cold and temperate latitudes around Antarctica and in a band across north pacific) and a type of zooplankton called radiolaria (found beneath the warm waters of the equatorial latitudes). Their skeletal remains are the dominant components of diatomaceous and radiolarian ooze. Siliceous material will dissolve at all depths, but it dissolves most rapidly in shallow, warm water.
Know the physical properties of water that we discuss in class. These include: physical states, specific heat, surface tension, density, dissolving ability.
Physical States - gas, liquid, solid. Addition or loss of heat breaks or forms bonds between molecules to change from one state to another. The only substance that occurs naturally in three states on Earth's surface. Important for the hydrologic cycle and the transfer of heat between the oceans and atmosphere. Specific Heat - One calorie per gram of water per C degrees. Highest of all common solids and liquids. Prevents large variations of surface temperature in the oceans and atmosphere. Surface Tension - Elastic property of water surface. Highest of all common liquids. Important in cell physiology, eater surface processes, and drop formation. Density - Mass per unit volume: grams per cubic centimeters, g/cm3. Density of seawater is controlled by temperature, salinity, and pressure. Controls the ocean's vertical circulation and layering. Affects ocean temperature distribution. Dissolving Ability - Dissolves solids, gases, and liquids. Dissolves more substances than any other solvent. Determines the physical and chemical properties of seawater and the biological processes of life-forms.
The salt balance in the ocean has been the same for 1.5 billion years. How is this maintained - where does the salt come from and where does it go?
Runoff from land adds an abundant amount of salt to the ocean. For the oceans to remain the same salinity, the rate of addition of salt by rivers must be balanced by the removal of salt; input must balance output. Salts can be removed by being blown ashore, evaporation and organisms.
Explain the effect of increasing and decreasing the salinity, temperature, and pressure on the density of seawater.
Salinity - When salts are dissolved in water, the density of the water increases because the salts have a greater density than water. Temperature - when water is heated, energy is added and the water molecules speed up and move apart. Density of warm water is less than that of cold water, and warm water floats on cold water. When water is cooled, loses heat energy and the water molecules slow down and become closer together. Because cold water is denser than warm water, it sinks below the warm water. Pressure - Pressure in the oceans increases with increasing depth. Water doesn't compress much; has little effect. The pressure effect is small enough to be ignored in most instances except when very accurate determination of seawater density is required.
What is the difference between sea ice and icebergs?
Sea ice - as seawater begins to freeze, a layer of slush forms covering with a thin sheet of ice. Icebergs - massive, irregular in shape, and float with about 12% of their mass above the sea surface. Formed by glaciers.
Silicate is a nonconservative constituent of seawater and does not obey the principle of constant proportions. Explain why.
Silicate is closely related to the life cycle of living organisms. Populations of organisms remove ions during periods of growth and reproduction, reducing the amounts in solution. Later, the population declines and decay processes return these ions to the seawater.
What is the study of the ancient ocean history through analysis of sediments called? How can this study be used to understand Continental Drift?
Study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Study microfossils; can figure out when land split and oceans formed.
Specifically explain how the properties of the water molecule affect (a) surface tension and (b) the dissolving ability of water?
Surface tension - properties of water molecules stick together, cohesion
Explain the characteristics of the Antarctic Ozone hole.
The "ozone hole" is the result of a large-scale destruction of the ozone layer over Antarctica that occurs when temperatures in the ozone layer drop low enough for clouds to form. This hole is usually largest in September, the size and shape of the ozone hole vary from year to year with natural variations in the temperature of the stratosphere (where clouds form).
Explain the Coriolis effect and describe its direction in Northern and Southern hemisphere.
The deflection of moving air relative to Earth's surface is called the Coriolis Effect. Both moving air and moving water are deflected relative to their intended direction of motion - to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
What happens to the density of pure water when it reaches the freezing point?
The density of pure water reaches its maximum at 3.98 degrees C. Pure water is free of dissolved gases. Density decreases quickly and then starts to go back up.
Explain why global warming is enhanced by the accumulation of CO2 and other greenhouse gases in the atmosphere.
The increase will warm the Earth and alter its average heat budget by reducing the surface heat loss to space by long-wave radiation to space in order to maintain the heat budget of Earth and atmosphere systems.
What is ocean acidification and what is causing it? List some of the effects.
The increasing concentration of CO2 in the water is causing a decrease in the pH of the water. The increase in ocean acidity could have a major impact on shallow-water marine organisms that build shells of calcium carbonate (which could dissolve rapidly in more acidic water).
Explain how pH varies relative to the concentration of CO2 in the water. What is a buffer?
The lower to concentration of CO2 in the water, the higher its pH and the more alkaline it becomes. A buffer is a substance that prevents sudden or large changes in the acidity or alkalinity of a solution. If some process changes the concentration of hydrogen ions in seawater, causing the pH to rise above or fall below its average, or mean value, the buffer becomes involved in chemical reactions that release or capture hydrogen ions, returning pH to normal.
What would happen to sea level if all the ice melted? Assume that ocean area doesn't change and that ocean temperature stays the same.
The sea level would rise nearly 70 meters.
Where do you find submarine canyons and how do they form?
These are steep sided and have a V-shaped cross section. They are formed by moving flows of sediment and water called turbidity currents. Found on the continental slopes.
Why does the intensity of radiation per square meter of ground vary with latitude?
Vary with latitude because the solar radiation per unit of surface area decreases with increasing latitude in each hemisphere, because the greater the latitude, the longer the distance through the atmosphere the suns rays must travel.
Describe a turbidite.
a sediment or rock deposited by a turbidity current. Turbidites are graded deposits, with the largest particles in the deposit at the bottom of the turbidite and the smallest at the top of the turbidite.