Volcanoes: Structure and Types

Volcanoes: Structure, Types, and Activity

• Volcanoes and Earth's Interior: Volcanoes provide insights into Earth's inner structure. They are found on land and ocean floors. Volcanoes often exhibit precursory signs before an eruption. A volcano not producing lava can still be dangerous.

Main Vent of a Volcano

• Definition: The main vent is the central tube-like structure through which magma travels to the Earth's surface.

Parts of a Volcano (Referencing Figure 1.1)

• Magma Chamber (2): The subsurface region where molten magma collects.

• Vent (4/6/etc): The opening of a volcano from which magma erupts.

• Lava/Magma Flow (1): Flows of molten rock on the surface.

• Slope (3): The side of the volcano.

Different Types of Volcanoes

• Composite Volcanoes (Stratovolcanoes): Built from alternating layers of lava flows, ash, and pyroclastic material. Viscous (sticky) lava makes up these volcanoes.

• Cinder Cones: Formed from solidified blobs and particles of lava ejected from a single vent. Lava solidifies in the air and falls as cinders around the vent.

• Lava Domes: Made of extremely viscous, sticky lava that doesn't flow easily.

• Shield Volcanoes: Broad bases and gentle slopes formed by effusive eruptions of less viscous lava.

Classifying Volcanoes: Activity

• Classifying based on activity is by eruptive history: Volcanoes are categorized as active, inactive, or dormant based on their history of eruptions. The most important basis for classification uses documented eruptions

• Active Volcanoes: Exhibit volcanic activity within the last 10,000 years (meaning they have erupted in that time frame).

• Inactive Volcanoes: No recorded eruptions but have the potential to erupt.

• Dormant volcanoes: Have not erupted in a long time but have the potential to erupt,

Philippine Active Volcanoes

• Active volcanoes in the Philippines: Mayon, Kanlaon, Calayan and Hibok-hibok are active volcanoes in the Philippines

Volcanic Eruptions: Types

• Phreatomagmatic Eruptions: Characterized by an explosive eruption from the interaction of magma and water. Pyroclastics are emitted sideways in this scenario. A short-lived event but may be a forerunner to a larger eruption.

• Plinian Eruptions: Highly explosive eruptions that involve the ejection of large volumes of pyroclastic material, often reaching great heights; Mount Pinatubo eruption in 1991 is an example.

Signs of Impending Volcanic Eruption

• Volcanic Tremor (Seismic Activity): Important sign, seismic activity

• Groundswell/ Ground Deformation: Change in shape/elevation of the volcano flanks

• Crater Glow: Visible glow at the top of a volcano, may be a precursory sign of activity.

• Drying Vegetation: A sign that something is amiss

• Increased Rainfall (incorrect): Is NOT a sign

Explore the fascinating world of volcanoes, including their structure, types, and activity. This quiz will enhance your understanding of how volcanoes provide insights into Earth's interior and the various components that make up these geological formations.