Volconoes Flashcards
When does a volcanic eruption occur?
When solid, liquid or gaseous material from earth’s interior is forced to the surface.
Where do volcanoes generally occur?
Subduction zones, constructive boundaries and hotspots.
What is pyroclastic material?
Huge quantities of broken rock that erupt from a volcano
What are volcanoes classified as ?
Active - currantly erupting e.g Mount Etna, italy.
Dormant - possibility of erupting e.g mount St Helens USA.
Extinct - extremely unlikely to erupt again e.g Sugar Loaf Co. Wicklow.
parts of a volcano
magma chamber, cone, volcanic bombs, vent, secondary vent, ash layer, crater, ash cloud
What is basic lava?
55% silica or less. Runny, Less gas, which can escape easily. Gentle eruptions, constructive plate boundaries, hotspots.
what is acidic lava
70% silica or more. Sticky and pasty. Lots of gases. Cannot escape easily. Violent eruptions. Destructive plate boundaries
What us pumice
Lava is thrown up due to forces of exploding gases and lava can be whipped creating air bubbles.
How does water vapour and torrental rain come into volcanoes/volcanic eruption
Subduction zones, Sea water descends towards mantle and heated up. Water vapour rises into atmosphere. It cools and may form torrental rain. This rain may mix with volcanix ash and dust created a mudslide ( larhar)
How do Volcanoes form at destructive plate boundaries (subduction)
Heavier plate subducts and begins to melt at depth of 100km.
Water vapour and gases are released and are trapped in magma chamber which forces it to rise upwards.
Pressure builds and then becomes so great it burns through overlying rock and erupts.
Oceanic-Oceanic Collison
Two oceanic plates rise above sea level.
Repeated eruptions causes build up of materials and forms Volcanic Island Arcs. e.g japenese island arc
oceanic - continental
chains of volcanic arcs form. e.g The Andes Volcanic arc due to subduction of Nasca plate beneath south american plate
Volcanoes at constuctive boundaries.
Two oceanic plates separate from each other.
Fissues form
Magma rises through fissures and erupts onto sea floor.
Gases can escape easily and eruptions are gentle.
Lava comes into contact with sea water it cools and forms basalt.
Basalt build up form a mid ocean ridge e.g Mid Atlantic Ridge.
Volcanoes at hotspots
Hotspots are located away from plate boundaries.
Hotspots are hotter areas of earths mantle.
Magma melts through plate to form volcano.
A volcano then moves away from hotspot - extinct.
New volcano forms over hotspot e.g the hawaiian islands
Positive impacts of volcanoes.
Creation of land
Formed from volcanic material e.g Iceland (youngest country on earth) Due to North American and Eurasian plates separating and layers of basalt build up from eruptions on Mid Atlantic Rigde
