effects of volcanoes on the environment

1. MOUNT
MOUNT ST.
ST.
HELENS
HELENS
By: Laura-Lynne Mccook

2. Mount St. Helens, also known as
Lawetlat'la to the indigenous Cowlitz
people, is an active stratovolcano located
in Skamania County, Washington. It lies
52 miles northeast of Portland, Oregon,
and 98 miles south of Seattle. Mount St.
Helens takes its English name from that
of the British diplomat Lord St Helens, a
friend of explorer George Vancouver who
surveyed the area in the late 18th
century. The volcano is part of the
Cascade Volcanic Arc, a segment of the
Pacific Ring of Fire.
STRATOVOLCANO
STRATOVOLCANO

3. PLATE BOUNDARY MAP
As an Eastern remant of the Pacific Plate, the
Juan da fuca plate,has subducted beneath
continental North America the Cascade
volcanic chain has formed. The Mt.St.Helens
volcano has been active for around 40,000
years but the now damaged cone we see
today has formed over the last 2,200 years -
The largest explosion of Mt.St.helens
happened 3500 years ago which produced 13
times more material than in 1980.
The volcano is highly explosive and erupts in
the Plinian style like Vesuvius. Sudden violent
explosions are accompanied by towering
clouds of hot ash, dust and rocks thrown high
into atmosphere. Pyroclastic flows and volcanic
mud flows called Lahars flow down the
mountain at speed and consume the
surrounding landscape. lavas from basalt to
andesites have been erupted forming layers of
ash and lava.

4. 2
3
4
1
DIAGRAM EXPLAINED
Mt St Helens is on the plate boundary between Juan de Fuca and the North American
plates, the boundary is also a part of the Ring of Fire. The Juan de Fuca plate is an
oceanic plate and the North American plate is a continental plate. The two plates
became a destructive plate boundary.
When a continental plate meets an oceanic plate. The oceanic plate (Juan de Fuca)
descended underneath the continental plate (North American plate) as it is denser.
When the oceanic plate descends further and further under the plate reaching past the
lithosphere, it reaches the asthenosphere part of the upper mantle, the plate begins to
melt because of the friction between the two plates.
Once the plate has melted it turns into extremely hot, liquid rock, which is known as
magma. The magma then rises through the gaps of the continental plate and when it
reaches the surface it forms a volcano.
This process goes on for hundreds of thousands of years, as more years go by more
magma rises. In this case when the magma rose, gases couldn’t escape causing the
magma to build more pressure, which creates a big volcanic explosion/eruption.

5. The Mount St. Helens major eruption of May 18,
1980 remains the deadliest and most economically
destructive volcanic event in U.S. history. Fifty-
seven people were killed; 200 homes, 47 bridges, 15
miles (24 km) of railways, and 185 miles (298 km) of
highway were destroyed.Autopsies indicated that
most of Mount St. Helens' vicitims died by
asphyxiation from inhaling hot volcanic ash, and
some by thermal and other injuries.
On May 18 1980 Mt.St.Helens produced an
enormous lateral blast which obliterated
everything for 20 miles north of the
volcano. The summit decreased from
2930m to 2550m and a gaping crater
1.5km wide was created.
Effects on People

6. Short Term Long Term
The eruption damaged roughly 230 square miles of land around the volcano,
according to the USDA Forest Service. It destroyed 158 miles of highway, and
15 miles or railways, the USGS reported. Washington state worked to remove
about 900,000 tons of ash from highways and roads.
Within 6 years after the 1980 eruption, most lakes had returned to
conditions typical of undisturbed Cascade Range lakes. In sharp contrast,
terrestrial ecosystems, covered with nutrient-poor volcanic ash and rock,
had greatly diminished biological productivity after the 1980 eruption.
The lateral blast, debris avalanche, mudflows, and flooding caused extensive
damage to land and civil works. All buildings and related manmade structures
in the vicinity of Spirit Lake were buried. More than 200 houses and cabins
were destroyed and many more were damaged in Skamania and Cowlitz
Counties, leaving many people homeless.
Many Lodges closed down which had a massive impact on the economy
because there was nowhere for tourists to stay.
Many tens of thousands of acres of prime forest, as well as recreational sites,
bridges, roads, and trails, were destroyed or heavily damaged. More than 185
miles of highways and roads and 15 miles of railways were destroyed or
extensively damaged.
The Ash settled 15cm deep so when it rained, it produced alot of mud flows
and made it hard for trees and other crops to grow
Effects on the
Environment

7. Benefits of
living near a
volcano
tourists are attracted
to the volcano, which
increases money to
the local economy
Volcanoes can provide
people with many benefits
such as: volcanic rock and
ash provide fertile land
geothermal
energy can be
harnessed,
minerals are contained
in lava, eg diamonds -
these can be mined to
make money
which results in a higher crop
yield for farmers.
which provides
cheaper
electricity for
locals

8. IMMEDIATE RESPONSES
IMMEDIATE RESPONSES
The Portland District of the Corps of Engineers responded immediately to the unfolding crisis. It turned its attention
first to floods and to restoring navigability. Its neighboring districts in Seattle and Walla Walla conducted damage
assessments in the affected regions. Corps personnel raised levees along the Cowlitz. They cleared debris from the
Columbia and employed four hopper dredges and several contracted pipeline dredges to create an emergency
navigation channel that allowed over 75 percent of the normal shipping traffic to resume by mid-June. With the initial
emergency response successfully completed, the Corps turned to address mid-term problems such as flood threats
from impounded waters and the continued sedimentation and debris flows into the area’s rivers.
The volcano had disrupted the entire hydrological flow of the basin and, between June and November 1980, the Corps
instituted a number of response measures. Corps and contractor personnel worked around the clock to clear debris
and dredge navigation channels in the Cowlitz and lower Toutle Rivers, removing thirty-five million cubic yards of
sediment and restoring the pre-disaster flow rate of the Cowlitz. The Corps also raised levees in the region to protect
against potential flooding.

9. LONGER TERM RESPONSES
LONGER TERM RESPONSES
The eruption of Mount St. Helens has influenced volcanology in many ways, and the next step in
this evolution is the National Volcano Early Warning System, or NVEWS. In March 2019, USGS
was authorized by Congress to develop and implement NVEWS to more fully monitor volcanoes
and to warn and protect citizens of the United States from danger caused by volcanic activity.
When NVEWS is fully implemented, all hazardous U.S. volcanoes will be monitored at levels
consistent with the threat they pose to communities, infrastructure and aviation. Pro-active early
warning of a potential eruption is key to minimizing loss of life and economic disruption by
increasing the time that emergency managers can initiate mitigation measures, improve evacuation
alerts and better position resources for recovery. Earliest detection of eruption precursors with
multiple instrument types allows for more accurate forecasts of hazardous eruptive activity needed
by land managers and the aviation sector.