North Myrtle Beach - LS Home Page

A Geologic Expedition

We gathered our data from Cherry Grove Beach. Cherry Grove Beach is
located in the city of North Myrtle Beach, South Carolina. It is situated in
Horry County, which is near the border between North and South Carolina.

I. North Myrtle Beach Introduction
II. North Myrtle Beach Geologic History
III.North Myrtle Beach Data

The Geology Background

The
Bedrock
The bedrock
in the North
Myrtle Beach
area formed
during the
Pleistocene
Epoch.
North Myrtle Beach
http://www.dnr.sc.gov/geology/geology.htm

This map shows
both the bedrock
and fault areas of
South Carolina.
The majority of fault
zones are located
in North West
South Carolina. (http://sciway3.net/2001/sc-geology/Overview_of_SC_Geology.htm)

(http://sciway3.net/2001/sc-geology/Overview_of_SC_Geology.htm)
The Resources
The geologic resources found in the area around North
Myrtle Beach are crushed stone, sand, and clay.

Sand Content
The sand specimen from
Myrtle Beach is
predominantly quartz
(around 90%). There are
some grains of biotite
mica within in as well
(5%). Small shell
fragments were also
present in the sample (5%
organic). The sand was
made up of very small,
sub-angular grains.
Cherry Grove Beach
A close up of the sand at Cherry Grove Beach.
Although the majority of the
sand on the beach was
dredged from an area
offshore, a possible source of
sediment is the marsh
mouth, indicated by the star
on the map http://www.holidaycity.com/northmyrtlebeachhotels/map.gif

North Myrtle Beach is continuously being attacked by erosion. The beach needs to be
renourished repeatedly, especially due to hurricane. Also boats and jet skis going
through the marsh increase erosion. Locals have different ways of protecting their
homes from erosion.
Riprap: This pile of stones is
used to protect houses.
Although, somewhat unsightly, it
is less damaging to the beach in
front of it as it does not reflect
wave energy, but absorbs it.
Seawall: This is a wall
designed to protect homes from
erosion. However this is
damaging to the beach in front of
the wall because the wall reflects
the wave energy, increasing its
ability to erode the shore .

Fossils
When walking the shore of North Myrtle Beach
one may come across fossils such as the ones
pictured here. They are a type of bivalve mollusk
(clam). Their scientific name is Cucellae Sp. and
are relatively numerous in the Upper Cretaceous
marine deposits. In South Carolina, along Route
17, there are a few recovery sites.
Identification thanks to Dr. Mark Leney,
Assistant Professor at UMass
A view of the Myrtle Beach Fossils

More Fossils:
Shark Teeth
The shark teeth that are seen
on this slide are like those
that can be found within the
sands of North Myrtle Beach.
Since they are fossilized,
these teeth can be millions of
years old. They vary in size,
shape, and color.

The Geologic History

Geologic History Of South Carolina
(http://sciway3.net/2001/sc-geology/Overview_of_SC_Geology.htm)

The Events pertinent to the
North Myrtle Beach Area
The more recent events occurring during the Cenozoic
Era are more relative to the North Myrtle Beach area as
they are the events that formed the coast of South
Carolina.
These Events Include:
(http://sciway3.net/2001/sc-geology/Overview_of_SC_Geology.htm)
The most important
event in the
formation of North
Myrtle Beach is
what occurred
during the
Pleistocene Epoch
and later, when the
bedrock was
formed.

Earthquakes:
An Important Part of South Carolina’s History
In Myrtle Beach's more recent geologic history, there was a large scale earthquake. Known as
the Charleston Earthquake, it occurred on August 31st,1886
(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php). It had a magnitude
of 7.3 and an intensity of X
(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php). A rating of X means
"Some well-built wooden structures destroyed; most masonry and frame structures destroyed
with foundations; ground badly cracked. Rails bent. Landslides considerable from river banks
and steep slopes. Shifted sand and mud. Water splashed over
banks(http://geology.about.com/library/bl/blmercalli.htm)." There was 5 to 6 million dollars
in property damage and 60 lives were lost
(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php). It was the most
destructive seismic event to ever take place in this portion of the US and, historically, among
the strongest earthquakes in Eastern North
America(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php). Myrtle
Beach felt the shock quite severely
(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php). In fact, it could even
be felt as far away as Boston, Milwaukee, and
Bermuda(http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php).
This was not a one time occurrence (http://www.scearthquakes.com/). As well as there having
been several smaller scale seismic events, there are risks of another shock in South Carolina
and it could potentially be very damaging, as strong earthquake precautions have not been put
in place there (http://www.scearthquakes.com/). If a similar earthquake were to occur today,
Horry County (where Myrtle Beach is located) would experience an intensity on the Mercalli
Scale of XI meaning “Everyone feels movement. Poorly built buildings are damaged slightly.
Considerable quantities of dishes and glassware, and some windows, are broken. People have
trouble walking. Pictures fall off walls. Objects fall from shelves. Plaster in walls might crack.
Some furniture is overturned. Small bells in churches and schools ring
(http://www.scearthquakes.com/)." But many other places in South Carolina will receive much
more damage (http://www.scearthquakes.com/).
http://www.scearthquakes.com/
Aftermath of the
Charleston 1886 quake.
http://www.scearthquakes.com/

The Recent History
of North Myrtle
Beach
A beach nourishment project put into
action in recent years has had the
most effect on the beach itself. Sand
was dredged from the ocean bottom,
three miles offshore, and pumped
back onto shore to protect people and
property on the shoreline from
erosion
(http://www.sac.usace.army.mil/?action=programs.m
yrtle_beach). 750,000 cubic yards of sand
was spread over 8.6 miles of shore
(http://www.sac.usace.army.mil/?action=programs.m
yrtle_beach). This is not the first time the
Cherry Grove Beach area of North
Myrtle Beach has been part of a
renourishment project, but it is the
first time since to 1996-98 dredge
(http://www.sac.usace.army.mil/?action=programs.m
yrtle_beach). Beach renourishment is
not a permanent solution and the
process will need to be repeated. Also
the use of this solution to erosion
means that the face and shape of the
beach will be changing in the future
as well as it has been different in the
past.
Some of the equipment used to dredge
North Myrtle Beach’s Beaches.
http://www.flickr.com/photos/whatafarce/2920042639/

The Data

The Longshore
Current.
The longshore current is the
current created when waves are
refracted as they come into shore.
It is located in the surf zone and
moves parallel to the beach.
The longshore current of Myrtle
Beach the current runs west along
the beach and takes roughly a
minute and forty-five seconds to
travel thirty meters. This is a rate
of one meter per every three and a
half seconds.
We measured the longshore
current by throwing an orange
into the surf and timing how long
it took to travel across a thirty
meter length, which we marked
out on the sand.
http://www.bonappetit.com/tipstools
/ingredients/2008/04/orange_peel
An orange, like the
one we used to
measure the longshore
current.
The surf zone where the longshore current can be found.

The Marsh
Harold, a local
fisherman who
we became
friendly with.
Hannah and Julia kayaking in the marsh of North Myrtle Beach.

The Flora of the Marsh
We noticed long grasses associated with the
lower marsh:
Alterna flora
However, the plants we saw that were
associated with higher marsh areas
were different(circled in the picture).
Here small, shrubs and bushes may be seen,
such as the palmetto bush. Also small trees
grow in the even higher marsh areas.

As can be seen by the previous slide, there are differences in the flora seen in
high versus low marsh areas. As low marsh areas are routinely flooded with
saline water while high marsh areas are not, both cannot support the same
plants. In lower marsh regions grasses grow as they can live in with the saline
water that floods them daily. However, at high marsh areas small trees and
shrubs grow. These plants cannot survive the daily flooding with saline water.
Therefore the difference between plants growing in high versus low marshland is
how much saline water they can withstand.

Oysters are a vital part of the
marsh ecosystem. They anchor
the grasses’ root system and
prevent marsh erosion. However,
boats making land in the grasses
destroy these oyster beds and
make the marsh susceptible to
erosion.

High Tide Mark
Using evidence in the marsh it is
possible to determine where the
high tide level is.
If you examine the photo to the
right, a dark line is noticeable in
the marsh grasses. This indicates
where the tide comes up too.
Also, by observing the marsh for
an entire day, it is possible to see
the changes in water height in
relation to the grasses.
By using this evidence in the
marsh, scientists can determine
sea level changes.
Alterna Flora exhibiting a dark line (indicated
by the arrow) showing the height of the water
at high tide.

Here you can see the differences in water level that can be used by
scientists to detect sea level changes.

Beach Profile
Swash Zone
Berm
Foredune

The dune closest to the shore.

The part of the beach that remains dry.

The portion of the beach where the waves break.

Before we took the data for the first beach profile, North Myrtle
Beach experienced rainfall, which may have altered the profile of
the beach slightly.
These profiles, taken from the same spot on two different days,
vary slightly from eachother. One of the reasons for these
differences could be erosion associated with the recent downpour.
Also, this beach is a high traffic one, as the area is a popular
vacation spot, and human activity on the beach, such as walking,
sandcastle building, hole digging, ect, could have altered the
profile a bit from day to day. That could be the reason for the
sudden dip at the end of the Day Two Profile. One final reason is
that our measurements will not be perfect and some differences
could be accounted for by a margin of human error.
*Note that the data tables do not go to the proper number of
significant digits. The proper number of digits is one significant
digit after the decimal point.

Elevation (cm)
0
-50
-100
-150
-200
-250
-300
-350
Beach Profile Day 1
0 20 40 60 80 100
Foredune
Berm
Distance (M)
Swash Zone

Original Distance (m) Original Elevation Change Total Distance Change Total Elevation Change
0 0
1 -6 1 6
3 -5 4 11
1.5 -7.5 5.5 18.5
2 -22 7.5 40.5
3 -17.5 10.5 58
2 -16.5 12.5 74.5
2 -21 14.5 89.5
2 -25 16.5 120.5
2 -19 18.5 139.5
3 -22 21.5 161.5
3 -20.5 24.5 182
3 -9 27.5 191
3 -10 30.5 201
3 -17.5 33.5 218.5
2 -9 35.5 227.5
3 -17.5 38.5 245
3 -12 41.5 257
3 -9 44.5 266
3 -7 47.5 273
3 -3.5 50.5 276.5
3 -5 53.5 281.5
3 -4 56.5 285.5
3 -3 59.5 288.5
3 -3 62.5 291.5
3 -3 75.5 294.5
3 -3 78.5 297.5
3 -4 81.5 301.5
3 -5 84.5 306.5
3 -5 87.5 311.5
3 -4.5 90.5 316
3 -3.5 93.5 319.5
3 -3 96.5 322.5
3 -1 99.5 323.5

Elevation (cm)
Fordune
0
-50
-100
-150
-200
-250
-300
-350
-400
Beach Profile Day 2
0 20 40 60 80 100 120
Berm
Distance (M)
Swash Zone

Original Distance (m) Original Elevation (cm) Total Distance Change (m) Total Elevation Change (cm)
0 0
3 -10 2 10
3 0 5 10
3 -23 7 33
3 -12 9 45
3 -20.5 12 65.5
3 -20 14 85.5
3 -25.5 16 111
3 -23.5 18 134.5
2 -15.5 20 150
2 -24.5 23 174.5
2 -11.5 26 186
2 -11.5 29 197.5
2 -15 32 212.5
2 -20 35 234.5
2 -12 37 246.5
2 -10.5 39 257
2 -10 41 267
2 -9 44 276
3 -5 47 281
3 -4 50 285
3 -3 53 288
3 -3 56 291
3 -2 59 293
3 -3 62 296
3 -3 65 299
3 -3 68 302
3 -3 71 305
3 -5 74 310
3 -5 77 315
3 -4 80 319
3 -4 83 323
3 -4 86 327
3 0 89 327
3 0 92 327
3 -2 95 329
3 -3.5 98 367.5
3 -4 101 371.5
3 -3 104 374.5

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.
"Digital Geologic Data at the South Carolina Geological Survey." South Carolina Department of Natural Resources. Web. 7 Apr. 2010.
.
"Digital Geologic Data at the South Carolina Geological Survey." South Carolina Department of Natural Resources. Web. 7 Apr. 2010.
.
"Historic Earthquakes." U.S. Geological Survey Earthquake Hazards Program. Web. 18 May 2010.
.
Map of North Myrtle Beach. Digital image. Web. 24 May 2010. .
"Mercalli Earthquake Intensity Scale." About Geology - The Complete Guide to Earth Science and Geology. Web. 18 May 2010.
.
"Orange Peel: Ingredients : Bonappetit.com." Bon Appetit Magazine: Recipes, Menus, Cooking Videos, and Food Blogs. Web. 22 May
2010. .
"Overview of SC Geology." South Carolina SC - Genealogical and Historical Websites. Web. 7 Apr. 2010.
.
"SC Administrative Law Court - Decisions." SC Administrative Law Court - Home. Web. 4 May 2010.
.
SCEARTHQUAKES.COM. Web. 18 May 2010. .
"SCSB#395: Geology." Web. 22 Apr. 2010. .
"U.S. Army Corps of Engineers, Charleston District ? Myrtle Beach Nourishment Project." U.S. Army Corps of Engineers, Charleston
District ? Home. Web. 22 Apr. 2010. .