EMS-Managing natural hazards, page no 146
What are Shield volcanoes:
They are broad volcanoes with gentle slopes and are shaped somewhat like a warrior's shield lying flat on the Earth. Ex:
Mauna loa in Hawaii and volcanos in Iceland.
Shield volcanos differences:
Found on constructive plate boundaries and hotspots.
Cover a wide area with gentle slopes {2* to 10*}.
Up to 900m in height.
Formed by lava flows.
Magma has a low viscosity.
Eruptions are usually non-explosive and consist of mainly basalt lava flows from vent.
What are Composite{Stratos} volcanoes:
A composite volcano, also known as a stratovolcano is a cone-shaped volcano built from several layers of lava, pumice, ash, and tephra. Ex: MT ST Helens, USA and MT Pinatubo in the Philippines.
Composite volcanoes:
Found on destructive plate boundaries.
Conical in shape with steep slopes{10* to 30*} and narrow bases.
100-100m in height.
Formed by alternating layers of ash and lava.
Magma is viscous.
Eruptions are explosive but infrequent and consist of ash, shattered lava, volcanic bombs and gases. Lava flows are limited in extent because of the high viscosity of the magma.
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How do the slopes of composite volcanoes compare to those of shield volcanoes?
What are the primary hazards associated with composite volcano eruptions?
How do composite volcanoes form at convergent plate boundaries?
What is the significance of andesite lava in composite volcanoes?
What role do pyroclastic flows play in the structure of composite volcanoes?