EnhancedSpirit said:
7 Wonders of Mount St. Helens
1. Mountain rearranged beyond recognition in nine hours.
2. Canyons formed in five months.
3. Badlands formed in five days.
4. Layered Strata Formed in Three Hours.
5. River System Formed in Nine Hours.
6. Sinking Logs Look Like Many Aged Forests in Just Ten Years.
7. A New Model for Quicker Coal Formation.
The link above gives detailed information on these 7 topics.
I like Tawn suggestion of throwing back some links:jiggy:
http://www.fs.fed.us/gpnf/volcanocams/msh/
EnhancedSpirit should volunteer for the link below:
http://www.mountsthelensinstitute.org/sciencecoordjob.html
Formative years
According to geological evidence, St. Helens started growth in the
Pleistocene 37,600 years ago with
dacite and
andesite eruptions of
pumice and ash. 36,000 years ago a large
mudflow cascaded down the volcano (mudflows were very significant forces in all of St. Helens' eruptive cycles). Parts of this ancestral cone were fragmented and transported by
glaciers 14,000 to 18,000 years ago during the last
ice age. Repeated eruptions of
pyroclastic flows, pumice, and ash followed until about 6500 BC when the volcano went dormant for 4000 years.
Starting around 2500 BC eruptions of large amounts of ash and yellowish-brown pumice covered thousands of
square miles. This eruptive cycle lasted until about 1600 BC and left 18 inch (46 cm) deep deposits of material 50 miles (80 km) distant in what is now
Mt. Rainier National Park and trace amounts have been found as far northwest as
Banff National Park in
Alberta and as far southeast as eastern
Oregon. All told there may have been up to 2.5 cubic miles (10 km³) of material ejected in this cycle.
After 400 years of inactivity, St. Helens came alive again around 1200 BC. This cycle, which lasted until about 800 BC, is characterized by smaller volume eruptions. Numerous dense nearly red hot pyroclastic flows sped down St. Helens' flanks and came to rest in nearby valleys. A large mudflow partly filled 40 miles (65 km) of the Lewis River valley sometime between 1000 BC to 500 BC.
The next eruptive cycle began roughly around 400 BC and is characterized by a change in composition of St. Helens' lava, which diversified by adding
olivine and
basalt to the mix. Also different was the presence of significant lava flows in addition to the previously much more common fragmented and pulverized lavas and rocks (
tephra). Large lava flows of andesite and basalt covered parts of the mountain, including one around the year 100 that traveled all the way into the Lewis and Kalama river valleys. Others, such as Cave Basalt (known for its system of
lava tubes), flowed up to 8 to 9 miles (13 to 15 km) from their vents. Also around the 1st century, mudflows moved 30 miles (50 km) down Toutle and Kalama river valleys and may have reached the
Columbia River. Another 400 or so years of dormancy ensued.
Sometime around the year 500 small quantities of ash and lava erupted from St. Helens' north flank. This period ended with the emplacement of dacite domes, including Sugar Bowl around the year 800. from:
http://en.wikipedia.org/wiki/Mount_St._Helens