Source: McDougal Littell, a division of Houghton Mifflin Company. Developed by TERC, Inc., Cambridge, Massachusetts.
National K -12 Subject:
Lesson Plans Using this Resource:
Large oil spills are not a common occurrence. So, when a tanker runs aground or collides with another vessel and releases its cargo to the sea, it's often major news — especially when it occurs near land. The images in this interactive activity from McDougal Littell/TERC show major oil spills and the techniques and equipment used to limit damage to coastal and other affected environments. Simulations reveal how the effects of an oil spill are influenced by variables such as the nature of the coastline, weather, and the type of oil spilled.
When oil spills from a tanker, its behavior and impact can depend on several factors, including the proximity of the spill to shore, tides and currents, weather conditions, and the type of fuel spilled. Understanding how these variables influence a spill allows scientists to develop dispersion models that can help them prepare appropriate response strategies.
If a spill occurs in the open ocean, little can be done to contain and remove the spilled oil. Getting cleanup crews and equipment to the spill site is logistically challenging. Left alone, all but the thickest grades of oil will evaporate. What doesn't evaporate will generally coalesce and sink to the sea floor, where it may remain in the sediment for years.
In near-shore environments, tides and currents have a major impact on the behavior of a spill. Oil tends to float on the denser seawater, and it behaves much like a wooden raft: it is carried in and out with the tides and is moved laterally along a coastline by currents. Weather conditions, especially temperature and wind, also affect spill behavior. Cold weather tends to slow evaporation, whereas wind influences the speed and direction of a moving surface slick.
Very light oils, including jet fuels and gasoline, are readily identifiable from the air by a rainbow-hued sheen. They contain high concentrations of toxic compounds, most of which evaporate quickly. Because they spread so thinly and quickly, they are difficult to contain and remove from the water. Heavy crude oils, on the other hand, spread more slowly, with little or no evaporation or weathering. Thus it is possible — though challenging — to contain and remove these materials. However, if they reach a shoreline, they contaminate it with a heavy tar-like coating that can suffocate animals and plants on contact.
Dispersion models can help explain why certain inlets of a coastline will collect a large volume of oil while other coastal areas are spared contamination. Carefully prepared models can also provide a measure of warning to arrange protection for vulnerable habitats, such as marshlands and clam beds.
Loading Standards
Teachers' Domain is proud to be a Pathways portal to the National Science Digital Library.
Background Essay
Print Background Essay