Download Volcano Notes lesson 9 Unit 4

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*Read along pages 306­313 to help you complete this assignment! What is a volcano?
• A ______________________ is any place where gas, ash, or melted rock comes out of the ground. • Many volcanoes are _____________________ meaning an eruption has not occurred in a long period of time.
• Volcanoes form as rock below Earth’s surface melts. The melted rock, called _____________________, is less dense than solid rock, so it rises to the surface.
• _____________________, or magma that has reached Earth’s surface, and ash erupt form a _____________________, or opening of a volcano. On this diagram label: Ash cloud, Vent, Lava, Magma
What are the kinds of volcanic landforms?
• The _____________________ of a volcano and the composition of magma determine the type of volcanic landforms created. • Volcanic mountains are landforms built from materials ejected from a volcano.
• The _____________________ of lava determines explosiveness of an eruption and the shape of the resulting volcanic mountain.
• Shield volcanoes
• are volcanoes with _______________________ and gently sloping sides. • Shield volcanoes cover _______________________ area and are the result of mild eruptions.
• Cinder cones • are small volcanoes with _______________________ slopes. • They form from ash and pieces of solidified lava that fall around a small vent.
• Composite volcanoes • They are formed of alternating layers of hardened lava flows and _______________________ material, or ash and bits of rock that were ejected from the volcano. • Composite volcanoes commonly develop into large _____________mountains
• ________________ eruptions happen when lava flows from giant cracks, or fissures, in Earth’s surface.
• Because fissures have no ________________ opening, lava flows out the entire length of the fissure.
• Fissure eruptions produce a flattened layer of cooled lava called a _______________
• A ________________ crater is an opening or depression at the top of a volcano which is caused by eruptions.
• Inside the volcano, molten rock can be found in a ________________.
• When the magma chamber empties, the roof of the chamber can collapse and leaves a large basin­shaped depression called a ________________.
Compare the before and after caldera forms _________________________________________________________________
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Where do volcanoes form?
• Volcanoes can form at plate boundaries or within the middle of ________________________________, which are giant sections of lithosphere on Earth’s surface. • At divergent plate boundaries, where two plates are moving away from each other, ________________eruptions are likely to occur.
• At hot spots, which are far from any plate boundaries, ________________volcanoes, fissure eruptions, and cinder cones can occur.
• At convergent plate boundaries, ________________ volcanoes can occur.
Divergent boundaries
• At divergent boundaries, the crust stretches and gets thinner. • As it thins, the pressure on the crust and mantle rocks decreases. This causes magma to melt and flow.
• Divergent plate boundaries create fissure eruptions and ________________ volcanoes.
• Most divergent boundaries are on the ocean floor. They make a long chain of undersea volcanoes called a __________________________.
• When a divergent boundary is located in the middle of a continent, the crust stretches until a ___________ valley is formed.
Convergent Boundaries
• At convergent boundaries, one plate usually sinks beneath the other. The mantle above the sinking plate can melt to form magma.
• The magma rises to the surface and forms volcanoes.
• Magma at convergent boundaries has a high concentration of fluids, which form gas bubbles.
• Because of the magma’s high viscosity gas bubbles in the magma cannot escape, pressure increases. • Eventually, magma erupts explosively, forming________________ volcanoes or calderas.
**Compare the characteristics of Divergent –vs­ Convergent boundary Volcanoes
Volcanoes at divergent boundaries
Volcanoes at convergent boundaries
Hot spots
Hot spots are locations far from plate boundaries where a mantle plume, a column of extremely hot mantle rock, rises and produces volcanoes.
Example: ____________ Islands