After millions of years, the streams of Taroko Gorge still tell the story of its
formation. Both geological uplifting and erosion by the Liwu River have formed walls
hundreds of meters high, a phenomenon seldom found elsewhere in the world. In addition,
there are magnificent mountains, such as the pyramid-like Mt. Zhongyangjian, and the
dramatic Qilai Mountain.
The formation of Taroko Gorge involved many steps:
( 1 ) Formation of limestone
Before the existence of Taiwan, calcareous sediments were deposited
in the ocean. As time passed, new sediment kept accumulating on top of the old;
this, followed by lithification, formed limestone.
( 2 ) Limestone metamorphosed into marble
After the deposition of the limestone, layers of other materials
were deposited, burying the limestone. After a long period of time, the intense
pressure and subterranean heat caused the transformation of the limestone into marble.
( 3 ) Uplifting of marble
About seventy million years ago, the rock strata under the sea
were forced up to form mountains, including the Taiwan mountain ranges. At the same
time, the horizontal marble strata were also forced upright.
( 4 ) Further uplifting of marble
About four million years ago, the Philippine Sea Plate and the Eurasian Continental Plate collided, causing the mountains to rise up and
the marble stratum, covered by other strata, to rise with them.
( 5 ) Valleys formed by river erosion
During the millions of years that have passed, the action of rainwater
and streams has eroded a massive amount of rock. At the same time, the continents
have been rising, so the mountains have become higher and higher while the valleys
have become deeper and deeper.
( 6 ) Formation of Taroko Gorge
Because the exposed marble was hard and resistant, it did not easily
erode, so the resulting valley was narrow with very steep sides. This nearly vertical
valley we call Taroko Gorge.