Volcanoes Flashcards
What is a volcano
A volcano is a structure containing a magma chamber from which molten magma moves.
The magma travels up through a vent
and eventually out through a crater.
What is volcanic activity
Through this crater, hot ash, dust ,
volcanic rock bombs and molten magma
erupt
Magma which has moved out of the
crater is known as Lava.
Over time, a landform known as a volcanic cone
develops
Where does volcanic activity occur
The world’s volcanoes occur in three different
areas:
1. DIVERGENT plate boundaries: Where plates pull
apart, magma comes up through a crack.
2. CONVERGENT plate boundaries: Where plates
collide and subduction occurs magma may reach
the surface through a small opening between the
plates.
3. HOTSPOTS: Weakness at the centre of a plate.
What is the Pacific Ring of Fire
This is where over half of the world’s active
volcanoes are located.
It is located around the edge of the Pacific
ocean.
Many of the world’s major plates meet here.
The life cycle of a volcano
ACTIVE VOLCANO: The volcano is still erupting a
frequent intervals, e.g. Mount Etna in Italy
DORMANT VOLCANO: The volcano has been quiet
for a long time (10,000 years) but may erupt again,
e.g Mount Fuji in Japan
EXTINCT VOLCANO: The volcano has not erupted in
recorded history, e.g. Slemish Mountain in Co Antrim
Products of a volcanic eruption
- Lava
- Pyroclasts and Pyroclastic flows
- Poisonous gases
- Ash pumice and dust
- Water vapour
- Lahars
Lava
There are two types of lava that can come to
the earth’s surface: acidic and basic
Depending on which lava comes to the
surface will gives us different landforms
Acidic lava
This type of lava is produced at a destructive plate
boundary. It is sticky and moves slowly. As this lava is sticky, gases can build up causing
great pressure. When this magma is realised it erupts with a massive explosion. These eruptions create dome volcanoes e.g. Mt St Helens
Basic lava
This type of lava is produced at a constructive plate boundary. It is a runny type of lava and it flows quickly. These eruptions create shield volcanoes. E.g. Mauna Loa
Pyroclastic flows
Pyroclasts are hot ash and rock fragments that are
thrown out of the volcano…
Pyroclastic flows are flows of boiling clouds of ash and rock with poisonous gases…
They travel at speeds up to 200km/h
They destroy everything they meet
Poisonous gases
Carbon dioxide
Sulfur dioxide
All these gases are released from the volcano and
they result in people been suffocated
Ash and dust
The power of an eruption shatters rocks
down to dust within the vent and cone…
On eruption this dust and ash can be
thrown many km into the air..
Winds can send this dust across the
world..
Pumice
When lava is thrown from the
volcano air is sucked into it.
This air is trapped into the lava
when it cools (rock) and makes it
a light rock.
This is now known as Pumice.
Lahars
Lahars are debris flows or mudlows, composed of
pyroclasts, rocks, and water… VOLCANIC LANDSLIDES!
Lahars travel at a variety of speed depending on their size.
The larger the lahar the greater the speed (up 80kph). As lahars move they erode the hill sides
Extrusive volcanic landforms
These are volcanic landforms found on the
earth’s surface. These include:
Plateaus
Volcanic cones
Craters and caldera
