Geologists have shown that the east coast of the United States faces a serious tsunami threat from .
A. large earthquakes offshore of Portugal
B. volcanic flank collapse in the Canary Islands
C. break up of Antarctic ice shelves
D. meteor impact in the Mediterranean Sea
E. landslides along the white cliffs of Dover

A. Large earthquakes offshore of Portugal.

Explanation:

Large earthquakes in coastal areas can cause tsunamis, an example of which being the boxer day tsunami in 2004.

volcanic flank collapse in the Canary Islands.

Explanation: Volcanic flank collapse can be defined as the collapse of volcanoes, resulting from instability, which can lead to large landslides.

They are among the largest and most destructive process on earth as they destroy everything in their path.

Some research say a volcanic explosion on an island 3,500 miles away could push out a wall of water that would destroy much of the East Coast of the United States.