What is an iceberg? Why are they blue or green?
An iceberg is a large floating block of freshwater ice that has broken off the edge of a glacier and been carried out to sea; about 90% of its mass lies under the water. The bluish streaks of clear, bubble free ice often seen in icebergs results from the refreezing of melt water which fills crevasses formed in the glacier as it creeps over land. The ice is blue because of the natural light scattering characteristics of pure ice. Occasionally airborne dust or dirt eroded from land ends up on the glacier surface eventually forming a noticeably darkened brown or black layer (in any orientation) within the ice of a floating iceberg.
What type of information can scientists obtain from polar ice?
Polar Regions and some alpine areas are sufficiently cold that snowfall accumulates from year to year, building up as glaciers. As snow at the surface gets buried with time it gets compressed to form solid ice and this ice carries with it information about the climate when the snow originally fell. By drilling down into a glacier and recovering this old ice, the information can be used to help understand past climate.
The information obtained from ice cores can be divided into three types. The first of these types of information comes from the solid and dissolved impurities in the snow. Usually snow that falls in those places is almost pure water, but it still contains traces of dust, and pollutants from human activities. This information can be used to detect major environmental changes in the circulation of the atmosphere. The second type of information obtained from ice cores comes from bubbles in the glacier ice. These bubbles are formed as snow becomes compressed and the air between the flakes gets trapped.
The third type of information obtained from ice cores comes from the frozen water itself. In the oceans, one in about every 500 oxygen atoms is the heavy isotope, while one in about 70 hydrogen atoms is heavy. However as the water evaporates and is transported to polar regions, the mix of the heavy isotopes changes. These changes are mostly influenced by temperature and it turns out that by measuring water isotopes in ice cores researchers can infer temperatures when the snow originally fell. In the past 30 years, many ice cores have been drilled to study past climate.
What is fathom?
a fathom is a unit of length equal to 6 feet (1.83 meters), used principally in the measurement and specification of marine depths.
What is bathymetry? Is the ocean floor flat?
Bathymetry is the measurement of the depths of oceans, seas or other large bodies of water, typically using narrow swath acoustic systems. Some modern side scan type of sonar systems use two transducers per side to produce bathymetric, data along with wide area imaging. These systems, although producing both types of data, leave much to be desired when compared with systems dedicated to either one or the other. Co-registered side scan and bathymetric data from a single instrument is a goal of many sonar designers.
We now know that most of the geologic processes occurring on land are linked, directly or indirectly, to the dynamics of the ocean floor.”Modern” measurements of ocean depths greatly increased in the 19th century, when deep-sea line soundings (bathymetric surveys) were routinely made in the Atlantic and Caribbean. Such echo-sounding measurements clearly demonstrated the continuity and roughness of the submarine mountain chain in the central Atlantic (later called the Mid-Atlantic Ridge) suggested by the earlier bathymetric measurements.
How do scientist collect sediments?
What is sediment? Where they come from?
Sediment is material that settles to the bottom of a liquid. It is Solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water, or ice.
What does the odor of ocean sediments tell us? What is the significance of the rotten egg odor? What does the color of ocean sediments tell us?
The odor is from the gas hydrogen sulfide that is produced by bacteria below the surface of the marsh muds. The water in the bay is usually no deeper than five feet and composed of a mixture of fresh and saltwater. The fish and bacteria that live there quickly use up the oxygen dissolved in the shallow brackish water. Their biological activity prevents oxygen from seeping into the sediments, and the mud becomes anaerobic, meaning “without oxygen.” This is the dark layer of mud where hydrogen sulfide is produced. Most consumers such as fish and frogs need oxygen to live, but there are many kinds of bacteria that live best in the absence of oxygen. Most of the sulfur in marine waters is in the form of sulfate, and some bacteria live off of this kind of sulfur. These bacteria are called sulfate reducers because they convert sulfate into hydrogen sulfide. Our understanding of the near-shore environment becomes useful when we study the deep sea. Oxygen does not penetrate deep down into the mud at the bottom of the ocean. Sulfate reducers produce hydrogen sulfide in the ocean bottom much like they do in the salt marsh.