VOLCANOE AND ITS RELATION TO PLATE TECTONICS

VOLCANO


Volcano - It is a vent in the crust of the Earth through which lava, volcanic ash and gases escape. Mountains that emit volcanic products like lava, rocks, ashes, and gases from the interior of the Earth through its vents.

COMMON PARTS OF A VOLCANO

TYPES OF VOLCANOES in Terms of Structure 

Cinder Cone Volcano

  • Steep slope 

  • emits ash during eruption

Shield Volcano 

  • Wide base

  •   Emits lava

Composite Volcano or Stratovolcano 

  • Half way of having steep slope and wide base

  • Emits both ash and lava 

Types of Volcanoes in Terms of Activity

Active Volcano - These are volcanoes that are “currently erupting or are expected to erupt in the near future”

Dormant Volcano - These are “not currently erupting but have erupted within recordable history and are expected to erupt again in the future.”

Extinct Volcano - “These volcanoes are considered as dead and are not expected to erupt in the future.”

How do volcanoes form?

Formation of Volcanoes

  • When the tectonic plates move apart (diverge), magma will ooze out from the cracks and fissures of the crust that are moving apart forming vents. These will then lead to formation of new land masses, volcanoes and volcanic activities. On the other hand, when the plates move towards each other (converge), upon collision, the plate that sinks (subducts) will melt in the mantle. And where there is melting of the plates, formation of volcanoes occurs.

Plate Tectonic Theory

  • This theory states that the Earth is composed of several broken plates that continuously move either away, past, or towards each other. 

  • The modern version of the Continental Drift Theory of Alfred Wegener

  • the mantle is composed of semifluid molten rock that moves constantly in a cyclic pattern forming convection cells. As the molten rock moves in the mantle, with the extreme pressure, some of the molten rock escapes through the cracks in the crust and along the boundaries of the tectonic plates resulting in earthquakes and volcanic activities.

  • the most known tectonic boundaries that consist of many active volcanoes and where frequent earthquakes occur is the Pacific Ring of Fire.

Continental Drift theory (Alfred Wegener) (Oskin, 2017)

  • This theory states that the Earth was once composed of only one supercontinent called Pangaea. 

  • Through time, this supercontinent split into two sub-continents, Laurasia and Gondwanaland. 

  • Million years further, Laurasia split into a few smaller continents forming the continents in the northern hemisphere of the Earth. This includes Asia, Europe, North America, South America, and Africa. 

  • On the other hand, the continents of the southern hemisphere, Australia and Antarctica, are the two continents divided from Gondwanaland.

Convection Currents

  • Scientists believe that tectonic plates move because of convection currents that flow up from the core of the earth and circulate under the asthenosphere.

  1. Outer Core - Heat is generated in the earth’s core by the decay of radioactive elements and heat remaining from the formation of earth.

  2. Convection - This heat slowly rises through the mantle to the asthenosphere

  3. Ridge push - The intrusion of magma into an oceanic ridge pushes the plates away.

  4. Plates float on the convection currents of the asthenosphere.

  5. Slab Pull - the cooling slab of denser oceanic slab sinks into the subduction zone.