1 / 15

Volcanoes

Volcanoes. OBJECTIVES: Types of Magma Anatomy of a Volcano Types of Volcanoes. Viscosity. Viscosity : Resistance of a liquid to flow There are 3 types of magma. They range from very runny (low viscosity) to very sticky (high viscosity). Anatomy of a Volcano.

fairly
Télécharger la présentation

Volcanoes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Volcanoes OBJECTIVES: Types of Magma Anatomy of a Volcano Types of Volcanoes

  2. Viscosity • Viscosity: Resistance of a liquid to flow • There are 3 types of magma. They range from very runny (low viscosity) to very sticky (high viscosity).

  3. Anatomy of a Volcano • Lava erupts through an opening called a vent. • Over time, the cooled & solidified lava forms a mountain known as a volcano. • At the top of the volcano, there is a bowl-shaped depression that can vary in size: • Crater: Smaller in size • Caldera: Larger in size. • Over 1 km in size • Forms when top of volcano collapses into the magma chamber.

  4. Anatomy of a Volcano • Volcanic fragments thrown into the air during eruptions are called tephra. • Can be newly cooled & hardened lava, crystallized mineral grains, or pieces of volcanic cone. • Categorized based on size. • Dust Size: Small • Volcanic Bombs: Large, rounded tephra. • Volcanic Blocks: Large, angular tephra.

  5. Anatomy of a Volcano • Pyroclastic flow are clouds of gas, ash, & other tephra down a slope at incredible speeds. • A.K.A. Rapidly moving volcanic material! • Can cause death & tremendous damage!

  6. Types of Volcanoes • Shield • Cinder-Cone • Composite (Stratovolcano)

  7. Shield Volcano • Gently sloping sides • Nearly circular base • Forms when layers of basaltic lava accumulate during non-explosive eruptions • Low viscosity magma: Basaltic Magma • Ex. Hawaiian Islands

  8. Cinder-Cone Volcano • Forms when material ejected high into the air falls and piles up around the vent. • Usually has steep sides • Generally small in height • Has more silica than shield and large volumes of gases • Explosions are more severe than shields: Andesitic Magma

  9. Composite Volcanoes • Forms when layers of volcanic fragments alternate with lava. • Large amounts of silica and gas: Rhyolitic magma. • Much larger than cinder-cone. • Violently explosive: Harmful to humans & environment • Ex. Mt. Saint Helens

  10. Where Do Volcanoes Occur? • Most occur at plate boundaries • 80% along convergent • 15%along divergent • 5% occur far from plate boundaries.

  11. Convergent Volcanism • Circum-Pacific Belt • A.K.A. “Ring of Fire” • Volcanoes of the Western U.S., Japan, Philippines, & Indonesia • Ex. Mt. Saint Helens • Mediterranean Belt • Volcanoes of Italy • Mt. Vesuvius

  12. Ring of Fire

  13. Divergent Volcanism • Most occur along ocean ridges. • Plates are pulling apart and magma wells up into the gap, producing volcanoes and lava flows.

  14. Hot Spots • The volcanoes that are formed far from plate boundaries are formed because of hot spots. • Hot Spots: areas of intense magma temperatures. • As a plate moves over a hot spot, the temperatures melt the crust and the new magma rises to form volcanoes. • When this happens, you get a string of volcanoes • Ex. Hawaiian Islands

More Related