Mặt trượt đứt gãy Tam Sơn
The Tam Son Valley, extending in the northwest-southeast direction, is the product of fault activity that is believed to have begun about five million years ago. As a result, limestone beds formed at the sea floor during the Devonian period (about 400 million years ago) were severely sheared and crushed, at many places almost powdered.
In addition to the dissolution action of water, the valley gradually lowered down into a karst field, with karst towers and cones scattered over the residual karst field, including the legendary "Fairy Bosom".
The direct evidence of the fault here is the so-called "Earth’s cut in Tam Son" right at the road side, almost opposite to the "Fairy Bosom". Here, in the crushed limestone, exposes a steep, flat, reddish brown and fresh surface of a small "component fault" of the greater fault zone that formed the Tam Son valley - formed by the relative movement of the two "flanks" of the fault in opposite directions, squeezing into each other. The reddish brown on the "fault surface" is the color of iron oxide, deposited from infiltrating water.
The "Earth’s cut in Tam Son" one more time confirms how powerful Mother Nature is - She can crush stone into powder, cut sharply through stone like hot knife cutting through butter! This Earth’s cut has yielded the fertile Tam Son valley, so rich and abundant in both land and water, that indigenous people later came and settled down, creating their rich cultural identity both in legends and daily activities.
Management Board of Dongvan Geopark