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Geographer traces changes to landscape
One
line of evidence for lower sea levels around Newfoundland comes
from submerged forests. This spruce stump, excavated at low tide
near Burgeo, was radiocarbon-dated at 1,400 years old. Trees
generally cannot grow in saltwater conditions. Therefore the
sea 1,400 years ago must have been at least several metres lower
than today.
By Andris Petersens
SPARK Correspondent
What we see today is not the same as what we saw yesterday. Still,
the small changes in the environment may pass by our eyes unnoticed
and a century from now, everything may look as if we had never
been here.
Nevertheless the landscape has changed. To find out more about
those changes we have to explore past landscapes. According to
Dr. Trevor Bell, Geography, the Newfoundland landscape looked
much different 20,000 years ago than it looks today with land
covered in ice and the sea floor, such as the Grand Banks, exposed
as land.
At that time, most of mainland Canada was covered with a large
continental ice sheet while Newfoundland had its own smaller
ice cap. As the climate slowly warmed, the ice melted and retreated.
Today scientists are interested in the dynamics of ice retreat
and climate changes in the past to find out how large ice masses
like the Antarctic or Greenland ice sheets might respond to future
climate warming.
The growth and decay of ice sheets cause changes in sea level,
Dr. Bell explained.
“Sea level changes in Newfoundland are mostly the legacy
of the last glaciation. The source of water for these large ice
sheets is the oceans. So, as ice sheets grow, ocean volume decreases
and sea levels fall everywhere. At high latitudes, however, the
weight of the ice sheets cause the Earth’s crust to sink,
causing local sea levels around the ice sheet to be higher. Later,
as the ice sheet melts, the crust rebounds slowly. My work looks
at the pattern, magnitude and timing of these sea level changes
around the province.”
One way to document changes in sea level is to examine marine
features and sediments that relate to former shorelines and to
date fossil shells, driftwood and whalebone found in them.
On the Northern Peninsula, the sea level at the end of the last
glaciation was 140-150 metres higher than it is today. Much of
the coastal lowlands was below sea level. Gradually, the land
has emerged from the sea exposing islands and peninsulas. Meanwhile,
for the remainder of the island portion of the province, the
sea has been submerging the land, drowning islands and eroding
the coastlines. In such places as Stephenville, Port-aux-Basques
and Burgeo, the sea has risen 30 metres or so in the last 10,000
years.
Dr. Bell, together with Dr. Joyce MacPherson from the Geography
department, explores how the vegetation has changed since the
ice sheets retreated.
“It is a succession from pioneer species, to shrubs and
then trees, the forest itself evolves as the landscape changes.
We use the change in vegetation as a sort of proxy for climate
change and other types of environmental change. For instance,
our coastal climate is influenced by the Gulf Stream and Labrador
Current – the Gulf Stream being warm and the Labrador Current
being cold. If you have changes in the strength of those currents,
for example, then it may affect the climate, which may in turn
influence the vegetation. My graduate student, Nicola MacIllfhinnein,
is looking to see whether we can recognize these large-scale
environmental or ocean changes in the postglacial vegetation
record, using pollen preserved in pond sediments on the Grey
Islands, off the Northern Peninsula,” Dr. Bell said.
Dr. Bell also works closely with Dr. Priscilla Renouf, Archaeology,
on a collaborative project that started in 1997 when they received
a special new initiatives grant from vice-president (research
and international relations). This grant allowed them to start
the project and apply for NSERC and SSHRC funding.
By integrating cultural history, archeology, paleogeography and
sea level history, Drs. Bell and Renouf have located sites of
Maritime Archaic Indians, the oldest inhabitants of Newfoundland.
“One of our approaches was to do targeted archaeological
survey based on our knowledge of sea level history,” Dr.
Bell said.
One of the immediate successes of this collaboration was the
discovery of a large site in Port aux Choix. The Northern Peninsula
is the only place on the island where sea level has been constantly
falling since the ice retreated said Dr. Bell.
“If we are going to find the older shorelines and possibly
more Archaic Indian sites, it is going to be on the Northern
Peninsula, where the fall archaeological record should be preserved
above present sea level. Unfortunately, many of the older shorelines
of the peninsula are in the woods, not around the present day
coast. It makes field surveys challenging.”
Drs. Bell and Renouf are also interested in how ancient people
affected the local vegetation, how they used that vegetation,
how they located their sites on the landscape, and what was important
to them in selecting a site. In Port aux Choix, the Maritime
Archaic Indian cemetery today is on a peninsula in the centre
of the town but in the past it was on an island. For 1,000 years,
the Archaic Indians probably lived on the mainland while they
buried their dead in the cemetery. They were obviously living
on a beach that was poorly vegetated. Over time, as they kept
coming back to the site, vegetation developed starting with a
shrub forest and then eventually a full forest. There may also
be evidence of human impact on the vegetation.
“We have found a spruce log dated to the Maritime Archaic
period with cuts in it that look as if it has been worked. We
have also reconstructed the local vegetation history and at the
times when the site was occupied, we see dramatic changes in
the vegetation,” Dr. Bell added.
Over the next couple of years, Dr. Bell hopes to extend his work
from the west coast of Newfoundland to Labrador, where he will
continue to document past changes in our landscape and environment
and the history of humans on that landscape.