Natural Dam EarthCache
Natural Dam is located in the Natural Dam Recreational Area
which is located in the Boston Mountains of northern Arkansas. The
Boston Mountains form the southwestern edge of the Ozark plateau.
This area is deeply dissected by the many creeks and rivers which
have, over time, eroded away the rock.
This erosion process is what created the waterfall. Over time,
Mountain Fork Creek eroded the softer rock until it exposed the
more erosion resistant sandstone of the Atoka Formation which
formed a natural dam, hence the name. Typically, a waterfall will
retreat over time as the water erodes the rock creating a gorge of
recession (see diagram below).This is caused by the flow of water
over a more erosion resistant rock stratum to the softer rock below
creating an undercutting.
Waterfalls can be classified into ten basic types:
- Block: Water descends from a relatively wide stream or
river.
- Cascade: Water descends a series of rock steps.
- Cataract: A large, powerful waterfall.
- Fan: Water spreads horizontally as it descends while
remaining in contact with bedrock.
- Horsetail: Descending water maintains some contact with
bedrock.
- Plunge: Water descends vertically, losing contact with
the bedrock surface.
- Punchbowl: Water descends in a constricted form, then
spreads out in a wider pool.
- Segmented: Distinctly separate flows of water form as it
descends.
- Tiered: Water drops in a series of distinct steps or
falls.
- Multi-step: A series of waterfalls one after another of
roughly the same size each with its own sunken plunge
pool.
To claim credit for this EarthCache, you must visit
Natural Dam Recreational Area during daylight hours and use the
information in this listing as well as your own observations to
email us the answers to the following questions:
- Is there any undercutting present at the falls?
- Using your GPSr as a measurement tool, what is the width of the
falls?
- What type of waterfall is Natural Dam?
Include a photo of yourself (not your hand), or a member of your
team, holding your GPSr with the falls in the background in your
online log. Logs without the required photo will be deleted.
We hope you enjoy your visit to Natural Dam as much as we have
the many times we've been here. Please remember to CITO during your
visit to help show our appreciation to the Forest Service for
allowing us to place this cache.
- Special thanks to Angela Chandler of the Arkansas Geological
Survey.
- Photo courtesy of mooremonkeys.
This EarthCache was developed by Bronze EarthCache
Masters