Volcanoes

Volcanoes Forms new land and ocean floor Replenishes the atmosphere with gases and water vapor Destructive to society

Types of volcanic Eruptions Non-Explosive Eruptions Explosive Eruptions

Non-Explosive Volcanic Eruptions are the most common found on land and ocean floors can release huge amounts of lava, gases and mud Most of the ocean floor and Hawaiian Islands are from non-explosive eruptions

Explosive Eruptions Are much rarer than Non-explosive eruptions Can be very destructive Clouds of hot debris, gases and ash are rapidly ejected from the volcano

Volcanic features

Types of Lava Aa Pahoehoe Pillow Lava Blocky Lava

Aa Flows out quickly (low viscosity) and forms a brittle crust The crust forms into jagged pieces as molten lava continues to flow underneath

Pahoehoe Flows slowly like molasses (high viscosity) Has glassy surface, rounded wrinkles

Pillow Lava Forms when lava erupts underwater Forms round or pillow shaped lumps

Blocky Lava Cool, stiff lava that oozes from erupting vent does not travel far Forms jumbled heaps of sharp-edged chunks

Volcanic Hazards Pyroclastic Flows Lahars Ash fall Lava flows Fumaroles

Pyroclastic Flows Hot ash, dust and gases ejected from the volcano flows very fast (more than 200 km/h) down slope Temperatures can exceed 700 degree C

Pyroclastic Material Volcanic Bombs- large blobs of magma that hardens in the air Lapilli- little pebble-like bits of magma that hardens in the air Volcanic ash- tiny glassy (silica) slivers makes up most of pyroclastic material in eruptions Volcanic Blocks- very large pieces of rock exploded from volcano

Volcanic bombs

Lapilli Lapilli are spheroid, teardrop, dumbbell, or button shaped droplets of molten or semi-molten lava ejected from a volcanic eruption which fall to earth while still at least partially molten.

Volcanic Ash

Volcanic blocks

Lahars Lahars are volcanic mud flows made up of ash, melted snow, or water, rocks and debris that is picked up.

Ash Fall Volcanic ash fall consists of ash (small tephra), which are bits of pulverized rock and glass created by volcanic eruptions. The ash is carried by the upper winds and droped down stream from the volcano, sometimes thousands of miles away

Fumaroles A fumarole is an opening in Earth‘s crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide

Lava Flows

Types of Volcanoes Sheild Volcanoes Cinder Cone Volcanoes Composite Volcanoes

Shield Volcanoes Forms from Non-explosive eruptions Lava is thin and runny (low viscosity) Covers large areas and has wide bases and gently sloping sides Hawaiian Islands are shield volcanoes and Mauna Kea is taller than Mount Everest

Cinder Cone Volcanoes Small volcanoes with steep slopes generally non-explosive Made up mostly of pyroclastic material Sometimes forms in clusters or on the sides of other volcanoes Erodes quickly due to the loose pyroclastic material

Composite Volcanoes Most common type Can form from non-explosive or explosive eruptions Made up of layers of lava flows and pyroclastic material Has broad bases and gets steeper towards the top

Craters A funnel shape opening that generally is a circular depression in the ground caused by volcanic activity Usually on top of a volcano Can contain lava, pyroclastic material, water, or snow and ice in the crater

Calderas A collapse of a volcano that is triggered by the emptying of the magma chamber beneath the volcano, usually as the result of a large volcanic eruption Similar to craters, but much larger Often fills with water Yellowstone Natl. Park is a caldera