volcanoes and volcanism products of volcanism pyroclastic flows can have large amounts expelled by...
TRANSCRIPT
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 FLOWSNUÉE ARDENTE
Mt. Pelee,Martinique, 1908
VOLCANOES AND VOLCANISM
PRODUCTS OF VOLCANISM
PYROCLASTIC FLOWSMaterial 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.
Acid rainH2O + 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
VOLCANOES AND VOLCANISM
PRODUCTS OF VOLCANISM
SECONDARY VOLCANIC AFFECTS
Giant seawavesTSUNAMI 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 fromsuccessive eruptions.
2. VOLCANIC CRATER - steep-walled bowl-shapeddepression surrounding the vent from which volcanic material escapes.
VOLCANIC CRATER
VOLCANIC CONE
VOLCANOES AND VOLCANISM
Mount Ngauruhoe, NZ
Valley of Fires NationalRecreation Area, NM
VOLCANOES AND VOLCANISM
EFFUSIVE ERUPTIONS
Quiet non-explosive events.Produce basaltic lavas.Small amounts of pyroclastic material is produced.
CENTRAL-VENT ERUPTIONS
VOLCANOES AND VOLCANISM
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 LoaMauna Kea
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 escapeelsewhere producing a FLANK ERUPTION.
Kilauea on the flank of Mauna Loa, Hawaii.
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.