Page 28 - Super Earth Encyclopedia

VOLCANOES

Most volcanoes mark the boundaries between the FIRE MOUNTAINS
moving plates of Earth’s crust. Some erupt through A typical volcano is a tall cone topped by
spreading rifts where plates are moving apart; others a crater that erupts lava and volcanic ash.
erupt over subduction zones where plates are grinding These settle around the crater to build up
together. There are also hotspot volcanoes, fueled the cone. But some volcanoes are very
different, and may be hard to recognize.
by isolated heat currents rising beneath the crust.

Stratovolcano
ERUPTION TYPES Dark, Crack Flowing This type of volcano forms where one of
hardened lava lava Earth’s plates is slipping beneath another.
Volcanoes erupt in different ways It releases sticky lava that does not flow far,
depending on their geological and layers of lava and ash form a steep cone.
location. Oceanic volcanoes erupt
liquid lava made of melted mantle Lava
rock that flows easily. Continental Side vent Steep cone
volcanoes produce sticky lava that Fissure formed by layers
can block volcanic vents, leading In this type of eruption, spreading rifts may of lava and ash.
to explosive eruptions. There are create long cracks that erupt liquid basalt
also many varieties in between. lava. These occur mainly on the ocean
floors, but can also be seen in Iceland.
Fire fountain Lava bombs
erupts into Either a small are hurled
the air. or no ash cloud. into the air.

Side vent Lava spills out ARENAL VOLCANO
from the crater. Glowing lava tumbles down the flank of
Arenal, a stratovolcano in Costa Rica.
Shield volcano Gentle slope is formed
Strombolian Volcanoes that erupt from by runny lava.
In a Strombolian eruption, the lava is spreading rifts or oceanic Crater
stickier and contains more gas. The gas hotspots produce very fluid Smaller
Hawaiian expands rapidly when it reaches the crater, lava. This lava can flow a long side vent
Oceanic hotspot volcanoes erupt liquid blasting molten lava high into the sky. way before cooling enough
lava that flows quickly but quietly to turn solid, forming a
downhill from the crater. They may broad shield volcano.
also produce fire fountains of lava.

Medium-height PITON DE LA FOURNAISE
ash plume Rain of This shield volcano on Réunion Magma
Towering ash island in the Pacific Ocean is one of
Volcanic ash cloud the most active volcanoes in the world.
bombs
Lava

Vulcanian
When lava contains a lot of silica— Plinian
the mineral used to make glass—it is The largest and most explosive
so sticky that it often solidifies in the eruptions blast lava and ash high into
vent. This makes pressure build up, the air. The ash cloud may collapse and
causing rare but violent eruptions. surge downhill in a deadly cascade.

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