Volcanoes ( Earth Science )

From Filipi Know

Volcanism

geological process where hot molten rock from underneath the earth reaches the surface through an opening in the ground.

volcano

most recognizable form of an opening, where molten material flows out onto the surface during a volcanic eruption.

Convergent Boundaries

partial melting occurs in subduction zones, which are responsible for the heating and partially melting of the rocks in the overlying plate

volatiles

 (seawater, water from minerals, and other fluids) from the oceanic lithosphere, lowering the surrounding rocks’ melting temperature. The molten rock then starts to ascend to the surface in the form of volcanic activity.

Divergent Boundaries

When plates move apart, pressure in the lithosphere reduces

Hotspots and Mantle Plumes

As volcanoes move away from the hotspot, they become inactive, subside, erode, and drop below sea level. This image shows the ages of the Hawaiian Islands in millions of years.

Mantle Plumes

Areas where the mantle rises towards the surface

Hotspot

Surface manifestation of a mantle plume

Volcano Morphology

Different types of volcanoes have different shapes and sizes. However, most volcanoes share certain characteristics. Here is the anatomy of a generalized volcano

Magma Chamber

the reservoir of molten material in the Earth’s crust, replenished with magma from a deeper reservoir in the mantle

Main vent

pathway for magma to come

Crater

Bowl-shaped located at the summit of the volcano serves as opening of volcano

Second cone

smaller parasitic volcanoes
usually emit volcanic gas called fumaroles (openings in the earth's surface that emit steam and volcanic gases, such as sulfur dioxide and carbon dioxide)

Pyroclastic materials

any volcanic material
such as bombs, blocks, ashes, and others

Shield Volcano

• - Large dome- shaped volcanoes with broad gentle slopes and large craters.
  - fast-moving basaltic lava flows.
  - non-explosive

Cinder Cones

• are steeper and have smaller crater
  - Moderately explosive
  - short lifespan (common type of volcano)

Composite Volcanoes or Stratovolcanoes

• Symmetrical steep-sided cone-shaped morphology
  - andesitic lava flows (an extrusive usually dark grayish rock)
  - Eruptions tend to be violent explosive

caldera

forming large depression called a caldera

pyroclastic flow

rapidly-moving current of hot gasses and tephra (all pieces of all fragments of rock ejected into the air by an erupting volcano)

explosive eruptions

Lahars

volcanic material becomes saturated with water

Lava flows

spread out over large distances

aa flows (ah-ah

spiky and rough

pahoehoe flows (pa-hoy-hoy)

ropey appearance with smooth surfaces

pillow lavas

smooth rounded shapes

When hot molten materials reach the surface, we call these materials as _________.

Lava

Lava refers to the hot molten materials that reach the surface

_____________ have symmetrical cone-shaped morphology. Famous examples are the Mt.

Stratovolcanoes

Stratovolcanoes, also known as Composite Volcanoes, have symmetrical steep-sided cone-shaped morphology. Examples of Stratovolcanoes are Mt. Fuji and Mt. Mayon.

Which of the following describes what a caldera is?

a large depression formed when a stratovolcano collapsed from an explosive eruption

Caldera refers to a large depression that was formed when a stratovolcano collapsed from an explosive eruption

How many active volcanoes are there in the Philippines?

24

Out of 407 volcanoes in the Philippines, 24 are active volcanoes

How do shield volcanoes get their broad form?

accumulation of basaltic lava flows

Shield volcanoes obtained its broad form due to the accumulation of layers of runny, fast-moving basaltic lava flows.