Page 336 - Earth's Climate Past and Future

312 PART V • Historical and Future Climate Change

Elevation of beach
(m)
50 100 150
0

2000
14 C age (years) 4000

6000

A B
FIGURE 17-4 Old beach ridges (A) A series of old beach ridges surrounds Hudson Bay.
(B) The beaches increase in age with elevation because the land has been slowly rising for
7000 years. (A: Courtesy of Claude Hillaire-Marcell, University of Quebec, Montreal. B: Adapted
from W. R. Peltier and J. T. Andrews, “Glacial-Isostatic Adjustment. I. The Forward Problem,”
Geophysical Journal of the Royal Astronomical Society 46 [1976]: 605–46.)

Bedrock
forebulge
Displaced rises
bedrock

Last glaciation (21,000 years ago)
Global
sea level Higher Observed local
rising sea level rise
Relative
sea level rise FIGURE 17-5 Bedrock sinking
Sea caused by and sea level rise In regions
Interior sea level land sinking surrounding glacial ice sheets,
change
Bedrock True global relative sea level is rising rapidly
sea level
flowing Bedrock rise today. The continued flow of
back forebulge bedrock away from these areas and
collapsing into the former ice sheet centers
0
1900 2000 causes the land to sink and adds to
Year
Today the true global rise of sea level.