Continental slopes are one of three parts that make up the under-ocean margin surrounding the continents of the world. In this lesson, you’ll learn what they are, where they are, and what some of their characteristics are.
What Is a Continental Slope?
Picture the most awesome waterslide you can imagine. You step off dry land where the waterslide starts as a gradual slope, then it drops hundreds, if not thousands of feet, before leveling out again. On this waterslide though, you would be underwater the whole way and you might also encounter some unexpected canyons. This is what would await you if your waterslide took off from most shorelines of the world.
Between dry land and the floor of the deep ocean is the continental margin, which is made up of three parts. The first part you would encounter after stepping off dry land would be the continental shelf; it tends to have a gradual, gentle change in elevation. Next comes the continental slope, where there’s a precipitous drop. After the drop, where the angle levels out, is the continental rise. The point where the continental shelf turns into the continental slope, which is not usually a precise spot, is called the continental shelf break.
Features of Continental Slopes
The angle of continental slopes are not the same everywhere. Worldwide, the angle of the continental slopes averages about four degrees, but there are factors that affect the steepness.
When the land that borders the ocean shore has newer mountain ranges and a narrow continental shelf, the angle tends to be steepest. These steeper continental slopes are active margins, where tectonic plates are on the move. Oceanic trenches are frequently nearby, too. Areas where the continental slope is not as steep are usually along passive margins, where sediments build up and are eroded away.
Most of the continental slopes in the Pacific are steeper than those in the Atlantic, but the flattest continental slopes are in the Indian Ocean.Because of these features and others, continental slopes aren’t smooth like a waterslide would be. Muddy sediments, deposited by rivers that flow into the ocean, can build up.
These sediments then become irregularly eroded, forming submarine canyons. Just when you think you’re in for a smooth ride, you could hit some pretty serious bumps!
Continental Slopes Around the World
Worldwide, continental slopes take up an impressive amount of the earth’s surface. If you added up all the continental slopes, they would stretch for 200,000 miles. The width varies quite a bit, though the average continental slope is 25 miles wide. It’s quite wide in the North Atlantic near Newfoundland at 228 miles wide and narrow in the Mediterranean and Black Seas at just over 15 miles wide.
Altogether, the continental slopes take up 8.5% of the ocean floor – that’s a lot of space for a waterslide!
Beginning at the edge of the shore and walking into the ocean, you would first reach the gentle slope of the continental shelf, then the steeper descent of the continental slope, before flattening out at the continental rise. The continental slope is not always smooth and can have caves, trenches, and submarine canyons. The width and angle of a continental slope depends on things like nearby rivers, the age of mountains on nearby land, erosion, and the width of the continental shelf. In active margins, where tectonic processes dominate, the continental slopes are usually quite steep. In passive margins, where sediment deposition and erosion dominate, the continental slopes aren’t as steep.
Most continental slopes in the Pacific are steeper than the ones in the three other oceans.