Instructions

Read the page below and compare and contrast passive and active continental margins. I recommend making a Venn diagram in your notes to help organize your thoughts. The content will prepare you to answer questions on the next page.

Time Needed

About 15 minutes.

Learning Objectives

Recognize Earth’s major surface features
Describe the constructive and/or destructive geologic processes at each plate boundary

The Continental Margin

The image below is a cross-sectional perspective, also called a profile, of the continental margin representing the transition zone from the continent's shoreline to the ocean floor's abyssal plain. It includes the continental shelf, continental slope, and continental rise.

Cross-sectional illustration of the continental margin.

Passive Continental Margin

Passive continental margins exist where there is no plate boundary between continental and oceanic crust. In other words, the continental and oceanic crusts are part of the same tectonic plates. No plate boundary means there are no constructive geologic forces. Instead, destructive geologic processes dominate, and erosion has worn down the landscape. Passive continental margins are characterized by subtle topography along the coastline, no volcanic activity, little to no earthquake activity, and a wide continental shelf. The image below illustrates these characteristics.
Illustration of a passive margin.
Passive continental margin (By Joshua Doubek (Own work) [CC BY-SA 3.0], via Wikimedia Commons).

Active Continental Margin

Active continental margins include a plate boundary and separate continental from oceanic crust. Interaction of the plates along the plate boundary drives constructive geologic processes, such as tectonic uplift and generating magma, resulting in pronounced topography with hills, mountains, and volcanoes. Active continental margins generally have a narrow continental shelf. In the illustration below of an active margin the continental shelf is narrow, separating the trench from the shoreline.
An active continental margin.

Active continental margin (WikiCommons).

The map below shows the locations of an active continental margin along the western margin of South America. A trench separates oceanic and continental crust. The passive margin is along the eastern margin of South America, with no plate boundary between continental and oceanic crust. The continental shelf (indicated by the lightest blue color of the oceans) is relatively wide. Similarly, the transition from continental Africa to the Atlantic Ocean basin is a passive continental margin because no plate boundary separates the oceanic from the continental crust. One has to travel thousands of miles from the shoreline before reaching a plate boundary in the middle of the Atlantic Ocean.

World map showing plate boundaries and the locations of an active and passive continental margin.