Plate Tectonics: Vulcanicity

?
What are major extrusive landforms?
Volcanoes
1 of 62
Describe a fissure volcano. (what, where, type of eruption, example)
Occurs where an elongated crack in the crust allows lava to spill out over a large area. Constructive margins. Basaltic lavas and gentle, persistent eruptions. 2010 Eyjafjallajokul.
2 of 62
Describe a shield volcano. (what, where, type of eruption, example)
constructive boundaries and hotspots. Made of basaltic rock and eruptions are gentle and predictable. Gently sloping cones from layers of less viscous lava. Mauna Loa, Hawaii.
3 of 62
Describe a composite volcano. (what, where, type of eruption, example)
Found at destructive plate margins and created from layers of ash from initial explosive phases of eruption and subsequent layers of lava from the main eruption phases. Lava is rhyolitic. Mount Etna/Mount Vesuvius
4 of 62
Describe an Acid Dome volcano. (what, where, type of eruption, example)
Located on continental crust. Very steep sided and formed from very viscous lava. As it cannot travel far, lava cools quickly forming convex shaped volcanoes. Lava may solidify in the vent&be ejected later by explosion. Puy de Dome, France. Rhyolitic
5 of 62
Describe a Caldera volcano. (what, where, type of eruption, example)
Destructive margins, form when gases have built up beneath a blocked volcanic vent resulting in catastrophic eruptions that destroy the summit leaving a crater. caldera lakes. eruptions are v explosive and unpredictable. andesitic. Krakatoa indonesia
6 of 62
What volcanoes and lavas are found at destructive margins?
Acid Dome & Composite cone. More acidic & viscous lava.
7 of 62
What volcanoes and lavas are found at constructive margins?
fissure & shield volcanoes. Basaltic lava, low in silica.
8 of 62
What is an intrusive landform?
A feature formed when magma has risen through the crust but solidified before reaching the surface.
9 of 62
Name 4 intrusive landforms
Batholiths, Laccoliths, Sills, Dykes
10 of 62
Describe the formation of a Batholith
several 100km wide. Formed deep below the surface when large masses of lava cool slowly, producing coarse-grained igneous rock. Surrounding the Batholith is a metamorphic aureole, where original sedimentary rocks have been metamorphosed by pressure.
11 of 62
Give an example of a Batholith
Cornubian Batholith in the south-west of England formed approx. 280 million years ago.
12 of 62
Describe the formation of a Laccolith
Laccoliths are any type of igneous intrusion that has split apart two strata, resulting in a dome-like structure. Usually less than 16km in diameter.
13 of 62
Give an example of a Laccolith.
The Eildon Hills on the Scottish border.
14 of 62
Describe the formation of Dykes
Vertical intrusions of magma discordant to the existing rock strata, with horizontal cooling cracks. They often occur in groups known as Dyke Swarms. Erosion of the surrounding rock can leave dykes exposed as low ridges. Can stem from Batholiths.
15 of 62
Give an example of a Dyke
Kildonan on the Isle of Arran, Scotland
16 of 62
Describe the formation of Sills
Horizontal intrusions of magma concordant to the existing geological strata, with vertical cooling cracks which form hexagonal shapes that can be seen when later exposed by weathering. 30-60metres in thickness&can stem from batholiths.
17 of 62
Give an example of a Sill
Giant's Causeway in Northern Island, formed 60 million years ago.
18 of 62
What are minor extrusive landforms?
A feature formed by materials and gases breaching the Earth's crust.
19 of 62
Name 4 minor extrusive landforms
Geysers, Hot Springs, Lava Plateaus, Mud Volcanoes
20 of 62
Describe a Geyser and its formation
An intermittent turbulent discharge of super-heated water ejected and accompanied by a vapour phase. They create a tall gush or jet of upward water, created by pressure changes as a subsurface body of water is turned to steam by a shallow magma pool.
21 of 62
Where does the word Geyser come from?
From the Icelandic 'Geysir' meaning 'To gush'
22 of 62
Give an example of a Geyser and how often it erupts
Old Faithful in Yellowstone National Park, which erupts roughly every 90 minutes.
23 of 62
Describe Hot Springs and their formation
Found in areas where vulcanism does not produce constantly active volcanoes. They are geothermal pools of water heated by magma chambers in the crust. Often the water contains a lot of minerals such as calcium carbonate.
24 of 62
How many Hot Springs are found worldwide
Only 1000
25 of 62
Give an example of a hot spring and its average temperature
The Blue Lagoon in Iceland, 36C on average
26 of 62
Describe lava plateaus and their formation
A large flat expanse of land created by lava spreading across valleys and depressions, forming a relatively flat and featureless plain of solidified lava. Only created by low-viscosity basaltic lava. Acidic lava would not be able to travel as far.
27 of 62
Give an example of a lava plateau
The Lava fields in Iceland
28 of 62
Describe mud volcanoes and their formation
Occur when superheated water, like that found in a hot spring, mixes with muds near the surface, creating a bubbling cone-shaped mud volcano. They are formed from a mix of hot water and fine sediment, and are usually less than 1-2 metres tall
29 of 62
What are mud volcanoes also known as?
Boiling mudpots
30 of 62
Give an example of a mud volcano
Rotorura, New Zealand
31 of 62
Define 'Hazard'
A hazard is a naturally occurring event that has the potential to cause loss of life or property. Without posing a threat to people, they are simply just natural processes.
32 of 62
Give 6 reasons to live in a volcanic danger zone.
Fertile soil, tourism, geothermal heat, scenery, mining (coal/gold/silver), cheaper housing
33 of 62
What percentage of volcanoes are monitored worldwide?
Only 20%, mainly in MEDC's
34 of 62
Name 6 methods of volcanic hazard modification
Monitor activity levels, Hazard maps from evidence of previous destruction, education/evacuation procedures, land-use planning, environmental controls eg channel lava, ensure roofs are steep and strong to shed ash
35 of 62
name 4 primary hazards of volcanoes
Tephra, lava flows, volcanic gases, pyroclastic flows
36 of 62
What is tephra?
A general term for all pyroclastic materials ejected from a volcano, such as rocks
37 of 62
Why are volcanic gases dangerous?
Volcanic gases such as sulphur dioxide and carbon dioxide in excess can cause suffocation
38 of 62
What are pyroclastic flows?
A fast moving current of hot gas and volcanic matter (tephra). Can reach speeds of 450mph
39 of 62
Name 5 Secondary hazards of a volcanic eruption
Volcanic landslides, Lahars, Flooding via the melting of ice caps/glaciers, tsunamis, climatic change
40 of 62
what are lahars?
A fast moving current of water and volcanic ash and mud.
41 of 62
Name 3 ways of diverting or stopping lava flow
Detonating explosives, spraying large volumes of water to cool flow, construction of earth walls to divert flow
42 of 62
Where has the use of explosives been used to stop volcanic flow?
Twice on Mount Etna, to create a hole in the crater for the lava to flow through, away from civilisation
43 of 62
Where has water been used to stop volcanic flow?
Large volumes of seawater used when Eldfell in Iceland erupted
44 of 62
Where have earth walls been used to divert flows?
These are in place across the Hawaiian islands.
45 of 62
Name 7 prediction techniques
Satellites picking up heat signals, groundwater may rise in height & temp, GPS measuring ground movement, tiltmeter detects minute movements of the mountain, seismometer to detect strength & frequency of volcanic tremors, gas ratio, infra-sound
46 of 62
How does the gas ratio of the volcano help predict eruptions?
Hydrogen chloride will increase before an eruption
47 of 62
How does infra-sound help predict eruptions?
It can hear and record the magma rising in the chamber
48 of 62
How does the viscosity of the magma affect the hazard potential of the eruption?
The more viscous the magma, the greater potential for explosive eruptions, presenting the greatest hazards
49 of 62
What are the two main types of magma and what are their characteristics?
Basic (Very fluid, low in silica, high temp) and Acid (High viscosity, high in silica, lower temp)
50 of 62
What are volcanoes on constructive boundaries like?
Basic-type magma formed by the partial melting of mantle. Frequent but not violent eruptions
51 of 62
What are volcanoes on destructive boundaries like?
Acid-type lava formed via subduction and intense heat and pressure melting the plate. huge build up of pressure leads to violent eruptions. Long dormant periods.
52 of 62
What are volcanoes like on conservative boundaries?
As there is no creation or destruction of crust, no volcanic activity is found at these margins.
53 of 62
What are volcanoes like at Hot Spots?
Basic-Type magma, similar to constructive margins.
54 of 62
How are eruptions measured/ranked?
On the Volcanic Explosivity Index (VEI) which is similar to the richter scale for earthquakes (both are logarithmic), although lists form 0-8.
55 of 62
What is the lowest and highest classification on the VEI?
The lowest is a Hawaiian Eruption (effusive), and the highest is an Ultra-Plinian Eruption (mega-colossal)
56 of 62
How do frequency of eruptions affect the hazard potential of a volcano?
If eruptions are very infrequent, people will likely have no living memory of it, and so the perception of the risk is much lower. Therefore people will be less inclined to prepare for a volcanic event.
57 of 62
What is an example of a volcanic eruption in an MEDC?
Mount Etna, Sicily, 1991-1993.
58 of 62
What is an example of a volcanic eruption in an LEDC?
Monserrat, Caribbean, 1995-1997
59 of 62
Composite volcanoes are also called what?
Strato Volcanoes
60 of 62
Composite volcanic eruptions are most often called what on the VEI?
Vesuvian
61 of 62
Name a supervolcano
Yellowstone, USA
62 of 62

Other cards in this set

Card 2

Front

Describe a fissure volcano. (what, where, type of eruption, example)

Back

Occurs where an elongated crack in the crust allows lava to spill out over a large area. Constructive margins. Basaltic lavas and gentle, persistent eruptions. 2010 Eyjafjallajokul.

Card 3

Front

Describe a shield volcano. (what, where, type of eruption, example)

Back

Preview of the front of card 3

Card 4

Front

Describe a composite volcano. (what, where, type of eruption, example)

Back

Preview of the front of card 4

Card 5

Front

Describe an Acid Dome volcano. (what, where, type of eruption, example)

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Plate tectonics resources »