continental margins dr. michael j passow. where the ocean meets the land is not the real edge of...
TRANSCRIPT
Continental Margins
Dr. Michael J Passow
Where the ocean meets the land is not the real edge of continents
• Oceans cover parts of what once was land, and, in some places, what is now land was once part of the oceans
• The zone where continents and oceans meet is called the continental margin
Active Margins
• Some areas are geologically active• Many of these have deep trenches or are
seismically active (have many earthquakes)• The west coasts of North and South America,
from Tierra del Fuego to the Aleutians, are active margins
http://en.wikipedia.org/wiki/Active_margin
Passive Margins
• Other areas shown little geologic activity, so they are called passive margins
• Much of the East Coast of North America, from NJ to FL and continuing along the Gulf Coast to TX, is a passive margin
Active margins
• are relatively narrow• have many earthquakes• drop off into deep trenches
or have volcano chains• form the “Pacific Ring of
Fire” that extends from New Zealand through the Philippines, Japan, Alaska, and down the west coast through the Cascades, Middle America Trench, and Peru-Chile Trench
Passive margins generally
• are much wider• have few earthquakes and
no trenches• form along the Atlantic
coastlines• often have coastal plains
and continental shelves• the world’s great rivers
drain across passive margins (Amazon, Nile, Congo, etc.)
Profile of a Passive Margin
Passive margins often have relatively flat continental shelves, steeper continental slopes, and continental rises that gradually blend into flat abyssal plains
The NJ continental shelf is about 120 km (75 mi) wide, with the hudson Canyon, largest of many submarine canyons, cutting across it.
http://clasticdetritus.com/2007/12/02/sea-floor-sunday-6-hudson-shelf-valley/
The Hudson Canyon
• Like an “underwater Grand Canyon”
• More than 700 km long• As much as 12 km wide• Descends from about
100 m to more than 2,200 m below sea level
• http://en.wikipedia.org/wiki/Hudson_Canyon
Other Submarine Canyonshttp://en.wikipedia.org/wiki/Submarine_canyon
• West Coast canyons start very close to CA beaches and descend rapidly
Rutgers University Research about the NJ Continental Shelf
• IODP Expedition 313 (2009)
• Objectives included learning about changes in sea level over past 35 million years, and climate changes during this period
http://www.eso.ecord.org/expeditions/313/313.php
