Tearing Down Mountains IV:
Coasts and Sea-level Changes
GEOSC 10: Geology of the National Parks
Presented by Dr. Richard Alley
The Pennsylvania State University
Sept. 18, 1999
Landsat image of
Cape Cod. The Outer
Beach (magenta
arrow) along the righthand side of the Cape
is eroding back at a
few feet per year.
Some of the sand is
building out to the
south and north
(yellow arrows), but
some of the sand is
being lost to deeper
water, so the Cape is
shrinking.
All pictures in this slide
show, except this one, by
http://www.nasa.gov/centers/goddard/news/topstory/2003/0901natlpark.html
R. Alley, C. Alley, J. Alley or
K. Alley.
GEOSC 10 - Geology of the National Parks
One good tern…
deserves another.
GEOSC 10 - Geology of the National Parks
The great Nauset Marsh, viewed from the back porch of the Salt Pond
Visitor Center, Cape Cod National Seashore.
GEOSC 10 - Geology of the National Parks
A fish that doesn’t
watch out may realize
too late that he blue it.
Great blue herons,
Nauset Marsh.
GEOSC 10 - Geology of the National Parks
Salt
marshes
are highly
productive,
and
support a
diversity of
life…
including
sandpipers
(top) and
yellowlegs
(right).
Nauset
Marsh,
Cape Cod.
GEOSC 10 - Geology of the National Parks
Waves and tidal
currents move
immense
amounts of sand,
leaving beautiful
ripples, as shown
in these closeups
from First
Encounter
Beach.
GEOSC 10 - Geology of the National Parks
Nauset Light. The light
was moved in 1996, just
before the rapid erosion
of the bluffs along this
part of the coastline
dropped this historical
building into the waves.
Everyone with a long
memory of the Cape has
stories of things that
have been lost to the
encroaching sea.
GEOSC 10 - Geology of the National Parks
Great Rock, the Cape’s largest glacial erratic (big rock carried by the
glacier) attests to the ability of ice to move pieces of many different
sizes. The rock extends below the picture, and then about as far into the
ground as above.
GEOSC 10 - Geology of the National Parks
Herring gulls at sunset, First Encounter Beach, Cape Cod.
GEOSC 10 - Geology of the National Parks
Acadia and
surroundings.
The yellow
arrow points
toward the fjord
of Somes Sound
in Mount Desert
Island. The
dotted line
marks an area
of interest for
NASA and the
National Park
Service, and
regions beyond
have been
blacked out.
All pictures except
this by C. or R. Alley
http://www.nasa.gov/centers/goddard/earthandsun/nps_data.html
Credit: NASA GSFC & Y.Q. Wang at the Laboratory for Terrestrial Remote
Sensing, University of Rhode Island
GEOSC 10 - Geology of the National Parks
The Rockefeller-constructed carriage roads and their graceful bridges are
well-loved at Acadia, which offers wonderful opportunities for bicycling.
Dr. Alley and daughters Janet (left) and Karen for scale.
GEOSC 10 - Geology of the National Parks
View of the Maine coast from Cadillac Mountain, Acadia.
GEOSC 10 - Geology of the National Parks
Bass Harbor Head Lighthouse (left)
and Portland Head Lighthouse (top),
Acadia National Park and vicinity.
GEOSC 10 - Geology of the National Parks
Loons in rain, Seal Cove Pond, Acadia. The deep, glacially carved
lakes of the island are outstanding for kayaking and canoeing.
GEOSC 10 - Geology of the National Parks
Jordan Pond and the Bibble Mountains. The rounded granite summits
and U-shaped valleys are clear evidence of past ice.
GEOSC 10 - Geology of the National Parks
Even a rainy day can be enjoyable on the shore, as here
at Ship Harbor. Notice the “beach” is composed of cobblesized rocks.
GEOSC 10 - Geology of the National Parks
The no-beach granite coast of Acadia National Park in the
fog.
GEOSC 10 - Geology of the National Parks
Ice flow as indicated by the red arrow smoothed this
island, and plucked rocks off the lee or downglacier side to
the right.
GEOSC 10 - Geology of the National Parks
Coasting Down
the Coast.
Including a bit on sealevel change, some
disasters, and some
coastal processes, in
some beautiful
places.
All pictures by R. Alley
or taken from
government Web sites
as indicated. The image
of Cape Cod National
Seashore and
surroundings is from
Landsat 7.
http://www.nasa.gov/centers/goddard/news/topstory/2003/0901natlpark.html
GEOSC 10 - Geology of the National Parks
Raised delta, Milne Land, east Greenland. About 12,000 years ago, a
stream flowing to the left from beneath a glacier built the sandy fingers
of this delta out into the sea. Then, the ice melted, allowing the land to
rise, so the delta is now about 300 feet above sea level (sea is barely
visible to the far left).
GEOSC 10 - Geology of the National Parks
Two views of the Westport Jetty, Washington.
Longshore drift from the right has built up sand to
the right but caused erosion to the left of the barrier.
Also notice in the left picture that waves are slowed
by the shallower waters near the jetty.
http://apps.ecy.wa.gov/shorephotos/s
cripts/bigphoto.asp?id=GRA0397
and GRA0398. Washington State
Department of Ecology Shore
photos--the state photographed
their coasts, and makes those
pictures available to the public-what a great idea!
GEOSC 10 - Geology of the National Parks
http://coastal.er.usgs.gov/hurricanes/
katrina/photocomparisons/mainmississippi.html
Before-and-after photos of
the aftermath of Hurricane
Katrina, near Biloxi,
Mississippi. The antebellum
house (upper right) and pier
house indicated by the red
arrows were destroyed.
GEOSC 10 - Geology of the National Parks
http://coastal.er.usgs.gov/hurricanes/k
atrina/photocomparisons/chandeleur.html
Before-and-after photos of
the impacts of Hurricane
Katrina on the Chandeleur
Islands, about 100 miles
east of New Orleans. The
sites marked by the yellow
arrows can be identified in
both photos.
GEOSC 10 - Geology of the National Parks
Before-and-after photos
of the impacts of
Hurricane Fran (1996)
on Topsail Island, North
Carolina.
http://coastal.er.usgs.gov/hurricanes/
mappingchange/images/photos/onslo
w-fran.jpg
The house indicated by the
left yellow arrow largely
collapsed, that shown by
the right yellow arrow lost
its deck, and most of the
other houses and much of
the road were destroyed.
GEOSC 10 - Geology of the National Parks
Evidence of longshore drift of sediment, Scoresby Sund, Greenland.
The small stream valley flowing from the top (blue arrow) has been
dammed by sediment transported along the coast (between the red
arrows).
GEOSC 10 - Geology of the National Parks
Mudder Bugt, Milne
Land, east
Greenland. The
upper picture is a
slightly turned closeup of the top part of
the lower picture.
Sand from the
braided stream
(lower right) is
reworked by waves
into the barrier
beaches and spits
seen, but the
beaches are
pierced by inlets.
GEOSC 10 - Geology of the National Parks
Satellite image of the Outer
Banks of North Carolina,
from USGS and NASA.
Streams flowing from the
left (two are indicated by
blue arrows) have been
flooded by sea-level rise in
their lower reaches. Sand
from the streams has been
built into barrier islands
(two shown by yellow
arrows). Although the area
covered by this picture is
much bigger, the features
are clearly almost identical
to those shown in the
previous pictures.
GEOSC 10 - Geology of the National Parks