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

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.

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 wiki/Hudson_Canyon wiki/Hudson_Canyon

Other Submarine Canyons 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 php

RU Coastal Ocean Observation Lab