Geology Reference
In-Depth Information
A
Recontructing Sea Level
EQ
HLS
HLS
HLS
i
ii
iii
former HLS
EQ: earthquake
EQ
HLS
HLS
EQ
iv
v
B
erosion surface
Coral
Stratigraphy
C
Relative Sea-Level History
10
0
-10
-20
-30
-40
-5
1920
EQ
EQ
HLS
Eroded HLS
HLS minimum
Sea-level fall
EQ
1930
1940
1950
1960
1970
1980
1990
2000
Year
Fig. 6.11
Tropical corals as paleoseismic recorders.
A. Geometry of annual bands recording interseismic submergence and coseismic emergence of coral heads. The
highest level of survival (HLS; tracked by black arrow) determines the height to which corals can grow and coincides
with the height above which corals would die due to prolonged subaerial exposure. (i) Upward growth indicates the
HLS is at or above the active layer. (ii) Outward growth in the absence of upward growth indicates the coral head is
at the HLS. (iii) Abrupt drop in sea level due to coseismic emergence during an earthquake (EQ) causes death and
erosion of the emerged part of the head, but outward growth of an annulus continues beneath the HLS.
