Mt. St. Helens SuccessionGoogle
Maps - Search for "Mt. St.
Helens" and zoom in to see the volcano, tagged "A". The satelite
image is one taken at the time of the eruption in 1980. NASA Fly-by of Mt. St Helens and time lapse animation
of succession |
 Mount St. Helens National Volcanic Monument |
Each research site in the photo sets below experienced a different set
of
conditions before, during, and after the eruption.
Observe the photo sets and compare
the
results of succession at the different sites over the 24 years since
the eruption in 1980 and 2004.
How have these factors affected the rate of succession at the different sites?
The severity of the blast at the site
The deposition of ash and pumice at the site.
The presence or absence of snow cover at the time of the
eruption.
The vegetation onadjacent sites.
Site #1 Pyroclastic Flow Deposits (Pumice Plain)
The first site sustained the full brunt of the blast that destroyed the forest and left the area completely buried in volcanic rock.
Site #2 Blowdown Forest with Plants Protected by Continuous Snowpack on May 18, 1980
The second site was a cool, north-facing slope that was covered by a thick layer of snow on the day of the eruption. The trees were all blown down, but the snow was not immediately melted.
Site #3 Blowdown Forest With No Snow Present on May 18, 1980
The third site was on a warmer south-facing slope where the spring snows had melted. All the trees in this area were blown down and the soil covered with a relatively light layer of volcanic rock and ash.
Site #4 Standing Dead Forest (Seared) Zone
The fourth study area was located in an area of blown down trees bordering on an area where trees had been killed, but the dead trunks remained standing. This area was near the edge of the park, bordering an area that had been salvage logged and replanted with new trees that soon reached reproductive age.
Site #5 Pre-Eruption Clearcuts
The fifth research area was located in an area of the forest that had been clear-cut a few years before the eruption. Little vegetation had managed to become re-established before the eruption. Trees in nearby un-cut forest were killed by the eruption, but left standing.
Be prepared to share your
findings with your classmates.