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Stage
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Description
|
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Stage 1: Initial
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Initial eruptions of
lava onto the ocean floor. Formation of pillow lava. Volcano may have steep
slopes up to 45 deg. Example - Loihi volcano (late stage 1). |
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Stage 2a: Shield Building - submarine
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Repeated voluminous eruptions
of pillow lava. volcano slopes 10-20 deg. No explosive activity due to
water pressure. |
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Stage 2b: Shield Building - sea
level
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Volcano reaches surface
with boiling water, explosive eruptions and fracturing of tephra to form
an island. |
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Stage 2c: Shield Building - subarial
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Permanent island formation.
Central and rift eruptions. Volcano slope of 3-10 deg formed by Pahoehoe
and Aa lava flows. Calderas and pit craters form and fill repeatedly. Only
a small percentage of tephra forms the volcano. Continued submarine and
sea level eruptions expand the volcano outwards. Examples are Kilauea and
Mauna Loa volcanoes. |
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Stage 3: Capping
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Explosive eruptions become
more common due to formation of more viscous lava. Steep cap with a slope
up to 20 deg is formed over the shield volcano. Eruptions become separated
by longer time intervals and finally end. Example - Hualalai volcano. Mauna
Kea volcano (very late stage 3). |
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Stage 4: Erosional
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The dominant process
is erosion by streams and waves. Canyons, valleys and seacliffs form. Corals
grow in shallow water around the island. |
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Stage 5: Renewed Volcanism
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Renewed volcanism may
occur after hundreds of thousands or millions of years. Erosion and reef
building continue. |
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Stage 6: Atoll
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The volcano eventually
erodes to sea level forming a flat island surrounded by coral reef. |
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Stage 7: Late Seamount
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Erosion overtakes reef
building and the island sinks below ocean surface. |
