lithoprobe logo
home | contact | search about | transects | publications | links | classroom/media 
media > slideset > the Growth of Canada >

Seismic record section of the central portion of line F. The prominent layering of the syn-rift deposits between 10 and 30 km depth are shown clearly.

Seismic and other data have now shown that this is the deepest rift on the planet. How deep was the rift? In some places more than 35 km, so deep that it almost split North America into two separate continents. An astounding 20 to 25 km depth of the gigantic rift valley were filled with interfingered lava flows and sediment carried in from the surrounding highlands (shown by the layered reflections below 10 km depth); then another 10 or more kilometers of sediments filled in after the rift had formed.
Below the rift, the crystalline crust had thinned to just one quarter of its original thickness. This enabled molten rock from even greater depths to force its way up — providing the enormous volume of volcanics that have been found, and perhaps completely fracturing the crust in some places.

previous page next image
home | about | transects | publications | links | classroom/media | search | contact