Volcanoes

Volcanoes Pyroclastic is a term used to describe any materials blasted out of a volcanic eruption The particles from smallest to largest are: 1. 1.Ash 2. 2.Cinders 3. 3.Lapilli 4. 4.Bombs 5. 5.Blocks Lapilli Bomb Block

Magma and Lava Magma is molten rock within the Earth Lava is molten rock on the Earth’s surface High viscosity lava (thicker) has more gas trying to escape  explosive eruption Low viscosity lava (thinner) has less gas  quiet eruption

Types of Lavas There are 2 types of lava flows: 1.Aa is a basalt with a high viscosity Forms higher viscosity, cooler basalt flows that creep along the ground They are blocky, sharp, and hard to walk on

Types of Lavas 2.Pahoehoe which forms from very hot and fluid, low viscosity basalt It is lava that forms very smooth, flat flows = ropy

Types of Volcanoes There are 3 different types of volcanoes that form when volcanoes erupt: 1.Shield volcanoes 2.Cinder cones or Pyroclastic cones 3.Composite cones or Stratovolcanoes

Shield Volcanoes These are low angle, nearly flat mountains of lava They occur with less viscous, fluid lavas This is the type that form Mauna Kea and Mauna Loa in Hawaii Erta Ale in Ethiopia

Cinder Cones These are higher mountains with steep slopes (a.k.a. Pyroclastic Cones) They have very explosive eruptions and create pyroclastic rock (cinders, ash, bombs, etc.) Mt Etna, Italy Pu`u ka Pele, Hawaii

Stratovolcano These are layered volcanoes and are often called composite cones They are made up of alternating ash/cinder layers and lava flows They are steep sided, high and usually continental Mount Mageik, Alaska Parinacota, Chile

Volcanic Landforms Volcanic domes generally form in the explosive type of volcanoes with a high viscosity magma to trap the gases and build slowly over time. Basalt plateaus are produced by magma with a lower viscosity that pours out over the land and are fairly flat Dome of Mt St Helens Dome of Jabal Abyad, Saudi Arabia on the basalt plateau

Volcanic Landforms Caldera = bigger than 1 km across, usually forms when a crater collapses back into the magma chamber, often have lakes form inside them Crater = less than 1 km across and circular Mt. Katmai, Alaska Crater in San Fransisco Volcanic Field in Arizona