The Petrified ForestThe Petrified Forest

October 2007

What does petrified mean?

• Greek root “petro”– Meaning “rock” or “stone”

• Example: From Harry Potter– People became PETRIFIED, turned into

stone

Mount St. Helena

• 3 million years ago• Suspected that Mount St. Helena erupted

7 miles NE• Sandy ash left as the soil• World’s Largest Petrified Trees - Redwood

http://en.wikipedia.org/wiki/Image:Mount_Saint_Helena_%282007-10-08%29.JPG

Located in Calistoga, CA

• All the petrified tree tops point in a Southwest direction away from the volcano

• Which supports the hypothesis that the blast knocked the trees over

Another Famous Volcano

• Mount St. Helens (WA)• Exploded in 1980• Trees were blown down parallel to a lateral blast

from the volcano and shows tops pointing away from source

• Trees are snapped easily like toothpicks

Mount St. HelensVisited in Summer 2006

After 28 years, hardly anything has grown back around the area of the volcano.

Water has carved throughthe ash to make rivers

Mount St. Helens has shown signs of life in the past few years. It has started smoking from its vent, number of earthquakes have increased.

Eruption of Mount St. HelensMount St. Helens Eruption October 2004 Eruption

• Trees at Mount St. Helens were not buried in ash

• They will not be petrified

Discovery

• Discovered in 1871, Charles Evans

• Found a stump of petrified wood while tending his cows

• 1914, purchased property by Ollie Bockee

• Developed the land by charging 50 cents admission

• Used funds to pay geology students to excavate more trees

• Discovered that these trees were the world’s largest Petrified Trees!!

How does wood become petrified?

• Water that has silicates in the ash seeped down into the gaps left behind by the decomposing tree fibers

• This replaces the wood cell by cell

• Wood is preserved from lack of oxygen

What are the wood cells replaced with?

• Crystalized silica

• Until the tree became stone

• Some of the silica has agatized into a colorful glass-like gemstone

What are silicates?

• Minerals, rock forming minerals• Such as quartz• Make up most of Earth’s crust• Petrified wood can have different colors

Following is a list of contaminating elements and related color hues:carbon - black cobalt - green/blue chromium - green/blue copper - green/blue iron oxides - red, brown, yellow manganese - pink/orange manganese oxides - black

• Petrified wood can preserve the original structure of the wood in all of its detail

• Tree rings and tissues

The Numbers (Mt. St. Helens – WA)

• Trees blown down: 4 billion board feet • Lava volume: 120 feet deep in places • Lava temperature: At least 1,300 degrees Fahrenheit • Slide area: 23 square miles • Property damage: 27 bridges, nearly 200 homes, 185

miles of highways/roads • Effect on Columbia River: Reduced channel depth

from 40 feet to 14 feet • Wildlife casualties: Killed in the blast were 7,000 deer,

elk and bear; all birds and most small mammals; 12 million chinook and coho salmon fingerlings in hatcheries and an estimated 40,000 young salmon in the wild

• Cost of damage and cleanup: More than $1.1 billion

http://seattlepi.nwsource.com/mountsthelens/summary.shtml

What caused Mount St. Helens eruption?

• 5.1 earthquake centered beneath the mountainMount St. Helen Facts and Information