Home | Session 4 | Shallow Marine Pg 1, 2, 3, 4, 5, 6, 7, 8
Shallow Marine Environments and Paleoenvironments: Reefs, Beaches and Basins
Presented
by Carol Tang
California Academy of Sciences
When we first started mapping the sea floor, we realized that the continents extended below sea level. In fact, our current shorelines and exposed continents are just an ephemeral characteristic-changes in sea level which have occurred many times in just the recent past dramatically change how much of the continents are exposed. Just 100 million years ago, for example, much of North America (including Texas, Arizona, Montana, Colorado, etc.) was underwater when sea levels were very high.
Here on the West Coast, we see that pattern as well-with a shallow shelf which extends below sea level. Here however, because we are on an active margin (review Session #1), it can be more complex that the pattern in the East. Follow this link to an image of canyons extending off the California coasts.
Take a look at this profile of the continent into the deep sea. On the left we see the extent of the continental land mass. The part of the continent below water is called the continental shelf. Offshore, we find a change in slope and that is called the shelf break. Then we get into the flat deep sea floor. Note however that this profile is highly exagerrated.
updated April 1, 2002
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