Rock Moved by Force: Eight Formations Built by Tectonic Stress

Thingvellir sits on the divergent boundary between the North American and Eurasian plates, which are pulling apart at roughly 2 centimeters a year. That slow separation fractures the crust and lets the valley floor subside between parallel fault scarps, with the Almannagja gorge along its western edge.

Here the Pacific and North American plates slide horizontally past one another. Across the Carrizo Plain that strike-slip motion has offset stream channels and ridgelines by tens of meters, leaving fault scarps and small sag ponds, and the 1857 Fort Tejon earthquake ruptured this stretch.

Where the old, dense Pacific Plate subducts beneath the smaller Mariana Plate, the seafloor is dragged down to the Challenger Deep, close to 10,900 meters below sea level. The great age and density of the descending plate is the usual explanation for a trench deeper than any other.

The collision of the Indian and Eurasian plates began roughly 50 million years ago and still pushes up the Himalayas. The summit is capped by the Qomolangma Formation, an Ordovician marine limestone laid down on the floor of the ancient Tethys Ocean and now the highest rock on land.

The canyon follows a zone of crustal weakness linked to rifting and faulting some 500 million years ago. Later uplift steepened the terrain, and the Fish River cut a gorge up to 550 meters deep along rock already weakened by ancient faults and joints.

These 36 domes are conglomerate, rounded pebbles and boulders cemented together as alluvial fan sediment about 550 million years ago. Tectonic movement tilted the beds steeply, and erosion of the softer surroundings left them standing as separate domes divided by narrow gorges.

This ring pattern roughly 40 kilometers across is not an impact crater. A subsurface igneous intrusion pushed up and deformed the overlying sedimentary layers, and erosion later stripped each layer to a different depth, exposing the concentric rings; the carbonatite is dated to about 104 to 94 million years ago.

The last stop is the deformation left by a different force. An asteroid strike about 2.02 billion years ago made a crater estimated at 250 to 300 kilometers across, and erosion removed the bowl, leaving an uplifted dome of deformed basement rock with shatter cones as the diagnostic evidence.