Educational resource_guide

TABLE OF CONTENTS

Lesson Plan - Your Field Trip to Ruby Falls

Geology of Ruby Falls

History of Ruby Falls

Environmental Education

Vocabulary List 
("Cave Communications")

Thought Questions Page

Quiz - Fill in the blank

Experiment - "Grow your own rock"

Quiz - Multiple choice cave terms

Cave crossword puzzle

Teacher answer page

Lookout Mountain is a landform that is noted for its unusual geologic phenomena. One of its unique features is Ruby Falls, an underground waterfall, located deep inside Lookout Mountain. The fascinating story of the formation of Lookout Mountain and Ruby Falls is told by the rocks themselves through what scientists call the Geologic Time Line. 

About 300 million years ago on an ancient sea bed, skeletons of small creatures accumulated forming layers of limestone. Successive layers of shale, sand and pebbly sand were deposited on top of the limy material and gradually these thick layers hardened. Scientists call this period in geologic time the Carboniferous Period. The Carboniferous Period was at the close of the Paleozoic Era, the oldest era in the geologic time line (before dinosaurs, mammals or birds had evolved). 

It was during this period that a powerful earthquake, or more likely a series of them, caused the layers of rock to bend or fold upwards forming what is now known as the Appalachian Mountain chain. As the brittle layers of limestone and sandstone rose from the ocean floor, cracks or crevices occurred. Scientists call these cracks or crevices faults or joints. Mountain ranges can form along normal faults and, it was along a fault of this type that Ruby Falls was formed. Many of these fault joints can be seen along the ceiling and walls of Lookout Mountain Caverns. 

Ruby Falls is located in the limestone layer of the mountain. As the subterranean streams found their way through the crevices, the water dissolved the limestone (a sedimentary rock) in a process called chemical weathering that released an acid called carbonic acid. This process along with physical weathering, which is the actual breaking of rocks by wind, water, or plants, aided in the formation of the cave by gradually dissolving the limestone.

Lookout Mountain Caverns actually consists of two caves. The lower cave is about 50 feet above the level of the Tennessee River and has no formations. The upper cave, containing Ruby Falls, lies directly above the original cave, but has no physical connection to it. The lower cave is permanently closed.

The formation of cave deposits (called speleothems) on the walls, floor and ceiling of the cave is a very slow process. The rate of growth varies from cave to cave; the average being one cubic inch every one hundred to one hundred fifty years. The largest formation at Ruby Falls, the Leaning Tower, is estimated to be between three and five million years old. The Ruby Falls cave is relatively dry which slows the formation's growth. The temperature in the Ruby Falls cave is about 60 degrees.

There are many different types of formations to be found in the Ruby Falls cave. The most common are stalactites, stalagmites, and columns. These formations are caused by water containing minerals such as calcium carbonate dripping down from the ceiling. They range in size from the tiny helictites found in the Hall of Dreams to the large column found in the Onyx Jungle. The rows of stalactites found on the ceiling are normally found along some joint or crevice in the limestone. 

Stalagmites, such as the Cactus and the Candle, are pillar-like formations that develop upward from the floor of the cave. Columns are formed where stalactites and stalagmites grow together such as the Onyx Column or the Leaning Tower. All of these formations are made up of calcium carbonate that has crystallized as calcite. 

There are several other types of formations that can be found in the Ruby Falls cave. Flowstone is thin sheets of calcite on the walls or ledges of the cave. It is formed by precipitation along a flat surface, permitting the water to run along this surface before falling. Frozen Niagara is the best surface example of flowstone in Ruby Falls.

Curtains, or drape formations, are formed by water emerging through a small joint or crack in the ceiling; the water evaporates before it has a chance to fall, thus building up a thin strip of calcite. Two examples of this at Ruby Falls are the Angel's Wing and the Arabian Drapery.

Helictites are fairly common in Ruby Falls, especially in the Hall of Dreams. They are a type of stalactite that grows without any regard to gravity. The crystals of calcite are not arranged in any symmetrical order, which causes the formations to assume a curved shape.

The truly amazing feature of the Lookout Mountain caves is not in the many formations that you see, but rather in the large vertical shaft at the end of the main passage that we refer to as the "falls room." A flowing underground stream falls from the very top of this shaft to form a 145 foot waterfall that collects in a pool on the floor of the cave. The volume of the waterfall depends on the amount of recent rainfall in the surrounding area. The water from Ruby Falls flows back through the cave and then down another waterfall (which is inaccessible) into the Tennessee River.