1. One half of the radioactive potassium-40 (K40) in an igneous rock has decayed to argon-40 (Ar40). According to the ESRT, about how many years ago was this rock formed?
(1) 1.3 x 109
(2) 2.6 x 109
(3) 3.9 x 109
(4) 9.8 x 109
2. State one difference between dating with radioactive isotope Carbon-14 and dating with the radioactive isotope uranium-238.
Carbon-14 can date organic remains.
Uranium-238 has a longer half-life.
VolcanoesFamous Eruptions
Volcanic debris
Types of volcanoes and lavas
Hazards and benefits of volcanoes
Lava Types
Viscosity- a fluid’s resistance to flow.
High viscosity- Low viscosity-
Slow moving
High silica content
Fast moving
Low silica content
Rhyholitic (felsic) Basaltic (mafic)
Volatiles- trapped gasses and liquids in a molten material
Increase explosiveness of a volcano
Stratovolcano (Composite volcano)
Mt. St. Helens
http://www.classzone.com/books/earth_science/terc/content/investigations/es0907/es0907page03.cfm?chapter_no=investigation
May 17, 1980 Harry Glicken, USGS August 13, 2005 Valerie Smith
Before and After the Eruption
Shield Volcano
Mauna Loa, Hawaii
Cinder Cone
Paricutin, Mexico
Caldera
Crater Lake, Oregon
Pyroclastic debris- deposits of volcanic origin
Volcanic debris
Blocks- greater than 64 mm in diameter
Lapilli- 2-64 mm in diameter
Ash- less than 2 mm in diameter
Bombs- greater than 64 mm in diameter (molten material)
Tuff- rock composed of compacted fragments of volcanic origin
Nuée ardente- fast moving, glowing, cloud of gas and ash
Volcanic debris
http://www.geo.mtu.edu/volcanoes/hazards/primer/pyro.html
Volcanic debris
Mudflow (aka: lahar)- the rapid downhill flow of a mixture or rock fragments, soil, and water.
Can travel tens to hundreds of miles away from the volcano
Associated with snow covered mountainsMt. Rainier (OR), Mt. St. Helens (WA)
http://www.classzone.com/books/earth_science/terc/content/investigations/esu301/esu301page08.cfm?chapter_no=investigation
Volcanoes Around the Universe
Io
Large moon of Jupiter
Similar size and density to Earth’s moon
Most volcanically active body in our solar system
Mt. St. Helens
Famous Eruptions:
http://www.classzone.com/books/earth_science/terc/content/investigations/es0907/es0907page03.cfm?chapter_no=investigation
May 17, 1980 Harry Glicken, USGS August 13, 2005 Valerie Smith
Before and After the Eruption
Mt. St. Helens Facts:• It is a stratovolcano (or composite volcano), located in
southwest Washington State.
• May 18th, 1980, 8:32 am (PDT). Eruption was triggered by a 5.1 earthquake centered beneath the mountain.
• The massive ash cloud grew to 80,000 feet (18 kilometers) in 15 minutes and reached the east coast in 3 days. Although most of the ash fell within 300 miles of the mountain, finer ash circled the earth in 15 days and may continue to stay in the atmosphere for many years.
• 57 people were killed as a result of the eruption. Of these, 21 bodies were never recovered from the blast zone.
Blow Down Forest
1981 2004
7,000 big game animals, 12 million Chinook and Coho salmon, and millions of birds and small mammals are believed to have died in the eruption.
Mt. St. Helens Eruption Picture From the Deck of Hoffstadt Bluffs Visitor Center
Mount St. Helens Re-born - Oct. 4, 2004
Current Eruptions December 15, 2007
Popocatepetl, Mexico
Giant plume of ash and steam spewed up to heights of 3,000 m (2 miles)
Volcanic ash from a single eruption can be deposited in a thin layer on the ground worldwide. Ash deposits can help with relative age dating of rock strata.
Risks Associated with Volcanos
• Loss of land, livestock, homes (etc), trees
• Weather is affected by ash particles in air
• Injuries, deaths of humans
Benefits of Volcanoes
• Soil around volcanoes is rich with minerals for plants/crops.
• Geothermal heating of homes close to volcanic regions.
• Hot springs.
• Tourism.