Tennessee Trails

Polk County, "The Ocoee River"

Kayaking on the Ocoee.

US Highway 64 follows the Ocoee River through the gorge, east of the town of Cleveland, Tennessee. Many interesting rocks can be seen from the highway in roadcuts and in the river bed starting near Ocoee Dam No. 1 (Parksville Dam). East of Ocoee Dam No. 3, the Ocoee River turns south and Highway 64 continues east to Ducktown.

The Geologic Story

The Earth is about 4.5 billion (4,500,000,000) years old. Over long periods of time, ancient continents have moved great distances, oceans have formed and later disappeared, and mountains have risen and worn away. Geologists read the history of the Earth, in part, by studying the rocks at the surface. Present-day locations of different types of rocks, and the minerals, textures, and structures (faults and folds) within rock units, are largely the result of plate tectonics the formation, movement, and collision of plates (continent-size, rigid slabs of solid rock).

• Ancient streams transported sand, clay, and gravel from a large supercontinent into a deep ocean (named Iapetus). The sediments spread out in alternating layers on the sea floor. A pile of sediments more than 6 miles (10 kilometers) thick accumulated and later hardened to form alternating beds of sandstone, shale, and conglomerate.
• Large copper deposits formed in the area we now know as Copper Basin, near Ducktown, Tennessee. Geologists think that these ore deposits probably formed from hot fluids escaping from deep within the Earth through vents in this ancient sea floor. Metal-rich "black smokers" discovered recently in the Pacific Ocean off the coast of Washington and Oregon may represent a modern analogy.

• A chain of volcanic islands moving westward on a crustal plate collided with the ancestral North American plate, causing huge sheets of rock to be thrust westward along faults or breaks in the rock layers. A second collision occurred later when the Iapetus Ocean closed and the ancestral African plate (called Gondwanaland) collided with the ancestral North American plate to create a supercontinent known as Pangaea.

Rocks buckled into folds and large blocks of rock slid over each other along the Great Smoky fault. Heat and pressure increased due to these collisions and transformed sedimentary rocks into metamorphic rocks. For example, shale became slate. These events built the present-day Appalachian Mountains.

• Light and dark gray bands in the rocks that we see along the Ocoee River Gorge today originally were layers of sediments that were deformed during this era. The lighter colored layers are coarser grained and harder than the darker colored layers. The hard, coarse grained layers form ledges that make many of the rapids in the river.

• Long after the last collision, the supercontinent began to split to form the modern Atlantic Ocean, which continues to grow wider even today. When this event began, dinosaurs were prevalent on Earth.

100 million years ago to the present (Cenozoic Era)

• Erosion by westward flowing water created the dramatic landscape and deep gorges along the Ocoee River and its tributaries. The Ocoee River Gorge cuts across the northeast trend of the Appalachian Mountains and has exposed a cross section through the rocks.

100,000 years ago (during the Quaternary Period)

• Evidence of modern humans on Earth appears in the geologic record.

150 years ago

• European settlers started mining and smelting metal ores in Copper Basin (Ducktown).

85 years ago

• The first dam (Ocoee Dam No. 1 or Parksville Dam) was completed on the Ocoee River to generate hydroelectric power. This dam created Lake Ocoee (Parksville Lake). USGS began monitoring the flow along the Ocoee River.

Today

• Geologic processes and human activities continue to change the landscape around you. Weathering from rain and snow erodes the hills and mountains as the rivers and streams carve deeper channels into the Earth. Weathering includes all processes (physical and chemical) that decompose bedrock and form soils.

Maps

Area surrounding the Ocoee River Gorge.

Topographic map of the Ocoee River Gorge area.

This map shows part of the Cleveland, Tennessee-North Carolina, 1:100,000-scale topographic map. This map is one example of the many different kinds of maps that the USGS and TVA provide for the public.

Folds and Faults

The Great Smoky fault intersects the Earth's surface near Ocoee Dam No. 1 (Parksville Dam). Faults and folds formed when older rocks were shoved over younger rocks during a continental collision more than 240 million years ago. The fault marks the boundary between two physiographic provinces: the Valley and Ridge province to the west and the Blue Ridge province to the east. Landforms are different on either side of the fault because rocks on the east side are more resistant to weathering and erosion than the younger rocks to the west. The fault is no longer active.

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