Fossil Ripple Marks--Still in the
Water
These formations can not be seen during times of high water or
flooding. Please do not attempt to visit this site when it is too
dangerous or the ripple marks are not visible due to high
water.
The Exposed Ripples, Northern Adams County
Photo by Ammosuperman
The Ripples
The strange looking rock formations at the bottom of this creek
bed are called “ripple marks”. They are formed by shallow water
flowing over a bed of sand or other sediments, or by wind-driven
wave action in shallow water, again over small sediments.
The ripples formed in shallow water by waves, (imagine small
waves lapping at the shore of a very shallow area of a lake) are
called wave-formed ripple marks. These are distinguishable by the
symmetrical shape of the individual ripples. Another type, called
current formed ripple marks are asymmetrical in shape with gentle
slopes on the up-current sides and somewhat steeper slopes on the
down-current sides of the ripples. Other more erratic ripple marks
are formed where two separate wave patterns, traveling in slightly
differing directions meet. These are classified as interference
ripple marks.
These patterns are usually small and close together, but not
always. Very large volumes of fast moving water can form very large
ripples. The Channeled Scablands in Washington State were formed
when an ancient, very large lake burst through its natural dam and
flooded many thousands of acres of land in a short amount of time.
The ripple marks it left can still be seen today and may be 100
yards in length or longer, with heights resembling small hills.
The formations seen at this site were almost certainly caused by
shallow, slowly flowing water moving over sandy or muddy areas. At
some point in the history of these formations, the ripples were
covered with other layers of sediment, without disturbing the
patterns we see today. In time there were many other layers
deposited here, compressing the layers by their own weight
effectively forming fossil wave marks in the rock.
Millions of years later, as erosion slowly removed the layers of
rock the ripple marks have been exposed and are as we see them
today. As erosion is an ongoing process, these remnants will
eventually disappear, worn away by the same processes that destroy
mountains, turning them into sediments. It is ironic that these
marks were formed in shallow water millions of years ago, and today
the rock that they have been preserved in makes up the bed of a
shallow stream. The water and wind created these formations, and
will destroy them in time.
The Rocks of the Area
These formations are made of limestone as are the other rocks
seen at this location. Limestone is a sedimentary rock that was
originally deposited as fine grained particles that settled to the
bottom of a large shallow sea which covered this area
millions of years ago. At this location the sea was so shallow that
the ripples formed by surface waves. In this water would have lived
snails, trilobites, brachiopods, and other invertebrates.
The loose rock here has been washed down from locations
upstream. As the rock that makes up the ripples break apart they
too will be washed farther down the stream bed.
Qualifications for Credit:
To get credit for this Earthcache email the answers to the
questions below and post a picture of you and your GPSr with
the ripple marks in the background. Failure to answer the
questions or logs with no pictures will result in the log being
deleted. If it is not possible to get a picture because of camera
problems, for instance the batteries died or you dropped your
camera in the water, email us first and we will work something
out.
Questions:
1. What process formed these ripple marks?
2. What type of rock is found at this location?
3. What is your estimate of the stream width at these
coordinates?
Credits and Ammosuperman EarthCaches
This EarthCache was created by a team of two Platinum EarthCache
Masters, Ammosuperman EarthCaches are a collaborative effort. We
have used resources such as the Internet and magazine articles as
well as personal experience in visiting the sites, as research
tools in its construction. Our goal is to learn more about our
planet and to pass along what we have learned to others having
similar interests. We hope you enjoy the experience.
