201 GLG 3.23.07 Why does relative sea level fall or rise? Absolute Land Rise/Fall Mountain-building Results from continents crashing together Results from continents and oceans crashing together Associated with LOTS of volcanic activity Can cause climate to warm or cool How? Clicker: How would a large volcanic eruption affect climate in the region right around the volcano? Answer: temperature would increase for a few days or weeks Clicker: How would a large volcanic eruption affect climate globally? Answer: the temperature will decrease Historic Eruption: Krakatoa, 1883 Energy of 4 eruptive events=200 megatons of TNT Third explosion alone was 150 megatons Hiroshima atomic bomb was only about 20 kilotons (.02 megatons) Krakatoa released 10,000 times the energy of the Hiroshima atomic bomb 1. The eruption was heard 4653 km away 2. Ash fell on Singapore 840 km to the North and on ships as far as 6076 km WNW Darkness covered some areas for 24 hours Giant 3. waves reached heights of 40 m above sea level Boats were picked up and carried ashore 4. at least 36, 417 people were killed, most by the giant sea waves, and 165 coastal villages were destroyed 5. Blue and green suns from fine ash and aerosol which circled the equator in 13 days 6. Three months after the eruption, ash had spread to higher latitudes Vivid red sunsets in New York Called out dire engines by mistake Unusual sunsets continued for 3 years 7. Volcanic dust acted as solar radiation filter Lowered global temperatures 1.2 degrees C Temperatures did not return to normal until 1888 Igneous Rocks: Last Depositional Environment Remember compositional terms? Felsic vs mafic Felsic:SiO2 (70%), Al, Na
Mafic: some SiO2 (50%), Fe, Mg, Ca Materials with MORE SiO2 move more slowly Resistance to flow: viscosity Recall: SiO2 has STRONG bonds Bonds must break for flow to occur On continents, where does most volcanic material come from?