VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM PYROCLASTIC FLOWS Can have large amounts expelled by volcanoes. Particles are generally large. Gravity tends to pull the pyroclastic material downhill. PYROCLASTIC FLOW or NUÉE ARDENTE. Trapped air and magmatic gases keep material suspended. Very low friction, velocities >150 km/hr (90 mi/hr).
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM PYROCLASTIC FLOWS NUÉE ARDENTE Mt. Pelee, Martinique, 1908
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM PYROCLASTIC FLOWS Material in nuée ardente may not cool completely before deposition. Soft material fuses with other particles. Forms solidified tephra. Called WELDED TUFF.
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM VOLCANIC MUDFLOWS Pyroclastic material mixes with water. Flows downhill as a LAHAR. Generally happens where abundant, loose, moist soil occurs. Tropical regions provide this setting. Helps if volcano is snow-capped or covered with glaciers. Ash and dust may actually enhance the potential for rain.
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM LAHAR Mt. Pinatubo, Philippines, 1991
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM SECONDARY VOLCANIC AFFECTS Acid rain H2O + SO2 H2SO4 + O2 Climate Influences Dust blocks sunlight. SO2 reflects and absorb radiation. 1815 - “The Year Without Summer” Eruption of Mt. Tambora, Indonesia Produced 60-80 mi3 of tephra.
VOLCANOES AND VOLCANISM PRODUCTS OF VOLCANISM SECONDARY VOLCANIC AFFECTS Giant seawaves TSUNAMI are produced by submarine volcanic eruptions and earthquakes.
VOLCANOES AND VOLCANISM ERUPTIVE STYLES AND LANDFORMS Two major features of all volcanoes. 1. VOLCANIC CONE - mountain or hill formed from successive eruptions. 2. VOLCANIC CRATER - steep-walled bowl-shaped depression surrounding the vent from which volcanic material escapes.
VOLCANOES AND VOLCANISM VOLCANIC CONE Mount Ngauruhoe, NZ VOLCANIC CRATER Valley of Fires National Recreation Area, NM
VOLCANOES AND VOLCANISM EFFUSIVE ERUPTIONS Quiet non-explosive events. Produce basaltic lavas. Small amounts of pyroclastic material is produced.
VOLCANOES AND VOLCANISM CENTRAL-VENT ERUPTIONS Basaltic lava flows from one vent. Flows out evenly in all directions. Produces a low, broad volcanic cone. Termed a SHIELD VOLCANO. Gentle slope with a broad summit. Found in Hawaii: Mauna Loa Mauna Kea
VOLCANOES AND VOLCANISM SHIELD VOLCANO Mauna Loa, HI
VOLCANOES AND VOLCANISM Lava may accumulate in the crater of the volcano. Crater fills to capacity and flows over the edge. Summit may then collapse into the evacuated area. Produces a CALDERA. CALDERA are typically big. Collapse may close the vent causing lava to escape elsewhere producing a FLANK ERUPTION. Kilauea on the flank of Mauna Loa, Hawaii.
VOLCANOES AND VOLCANISM CAULDERA Kilauea Caldera
VOLCANOES AND VOLCANISM Kilauea, Hawaii Flank Volcano
VOLCANOES AND VOLCANISM FISSURE ERUPTIONS ON LAND Series of linear fractures or fissures. Produces FLOOD BASALTS. Lava spreads out in thick layers. Thick layers are called LAVA PLATEAUS.
VOLCANOES AND VOLCANISM Columbia River Plateau lavas, WA.