EVIDENCE FOR ISOSTATIC
AND EUSTATIC SEA LEVEL
CHANGES
•What does isostatic
mean?
•What does eustatic mean?
•Which is changing in these
photos – land level or sea
level?
Aerial view of the raised beach
on the west coast of Arran.
Diagram from Arrran and the Clyde
Islands, Scottish Natural Heritage
Raised
beach
covered
with
coarse
shingle.
Old
stacks
Old cliff line
Raised beaches
Sea level 13,000 years ago
Raised beaches
Sea level 6,000 years ago
Cave
Sea
Rock
platform
Beach
Rock
Stack
Cross section though raised beaches
http://www.bbc.co.uk/scotland/education/geog/coastline/stand
ard/physical/features/sea_level/
Raised beach, Newton
Point, Arran
wave-cut
platform
old cliff line
King’s Cave, from the
Drumadoon sill
old cliff line
wave-cut
platform
King’s Cave
All the
caves are
full of very
rounded
pebbles ,
which have
the same
texture as
beach
pebbles.
The caves also
contain many marine
shells, which are
encrusted with
lichens. They are not
part of the present
marine deposits.
Raised sea stack, Bute.
Raised beach
Diagram from Arrran and the Clyde Islands, Scottish Natural
Heritage
Raised natural arch
Raised beach
deposits are
usually made
of coarse,
rounded
pebbles. This
deposit is
cemented with
iron. Godrevy
Point, Cornwall
Close-up
of the
Godrevy
Point
deposit
Marine platforms
Island above
old sea level
Penberth, Cornwall
Marine platform
River terraces
The Graded Steam
Idealised cross section
Idealised long profile
A
A
Upper reaches
B
B
Middle reaches
C
C
Lower reaches
Oblique view upstream
Sea level 1
Sea level 2
Sea level 3
Knick points
Terraces
River
Knick point
River terraces, NW Scotland
River terraces, Catacol
Drowned coast-lines
West coast of Norway
Fjord
Drowned
glacial
trough
Norwegian fjord
Drowned coast-lines
ria
South coast of Devon
Drowned river valley
Ria in Cornwall
Atlantic
Old cliff line
Raised
coastlines
Skogarfoss
Iceland
River Skoga, falling over
the post-glacial cliff
The End
THE
END