Geological History

A Colorado Wonder

Millions of Years in the Making

Long ago, warm shallow seas covered the Pikes Peak region of Colorado. In those ancient seas, abundant shell life thrived. As the sea creatures died, their shells fell to the sea floor and were broken up. Layer upon layer of seashells accumulated over millions of years. The weight of the overlying layers squeezed, compacted and cemented together the underlying layers into a solid rock called limestone. The process is similar to squeezing snow into ice.

The limestone in which Cave of the Winds was formed dates back almost 500 million years, deposited during the Ordovician period of Earth’s Paleozoic geological era in history.

About 70 million years ago, the seas that covered most of Colorado receded and the remaining limestone was uplifted, forming part of the present Rocky Mountain region.

The Cave of the Winds’ system of rooms and passages began to form approximately 4-7 million years ago, when the limestone was below the water table. Rainwater mixed with carbon dioxide and formed a weak carbonic acid. The acid solution dissolved away portions of the limestone, leaving behind small passageways that filled with water. As more limestone dissolved over thousands of years, the passageways grew larger and the rooms were formed.

After the water table dropped below the level of the cave system, the passageways and rooms filled with air, and beautiful speleothems, or cave decorations, began to form.

Stalactites were created within the rooms and passageways when calcium carbonate-rich water reached the ceiling of a room and started to drip. Each time a water droplet collected on the ceiling, a small amount of calcium carbonate crystallized into a calcite ring around the outside of the water droplet. As this process continued over thousands of years, icicle-shaped stalactites formed. Beneath dripping stalactites, stump-like stalagmites formed as the calcium carbonate crystallized and built up on the cave floor.

Flowstone, or frozen waterfalls, are beautiful curtain-like formations seen along the side of a cave room or passage. Flowstone forms when mineral-rich water flows down along the walls of the cave leaving the calcite behind.

Common Cave Geology Terms

  • Calcite — Calcium carbonate that crystallizes in hexagonal (six-sided) forms.
  • Column — The name given to a formation once a stalactite and stalagmite grow together.
  • Flowstone — A sheet-like deposit of calcium carbonate on the wall of a limestone cave. Also referred to as travertine.
  • Geology — The scientific study of the earth.
  • Limestone — A sedimentary rock composed of calcium carbonate.
  • Speleology — The scientific study or exploration of caves.
  • Speleothem — A cave formation.
  • Stalactite — An icicle-shaped deposit of calcium carbonate hanging from the roof of a limestone cave.
  • Stalagmite — A stump-like deposit of calcium carbonate rising from the floor of a limestone cave.


Geology of the Pikes Peak Region

Colorado geologic history shows the Pikes Peak area was covered by a vast, shallow sea. The sediments accumulated until they reached 40,000 feet. With time, chemical concretion, and pressure, they became sedimentary rock. Then during a period of orogeny (mountain-building), metamorphic rocks were formed. These rocks are called the Idaho Springs Formation and are located nearby in Idaho Springs, Colo.

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