Volcanoes

Question 1

Stratovolcano shape

Answer 1

Stratovolcanoes are tall, has a narrow base, and small crater, conical-shape with steeper sides.

Question 2

Shield volcano shape

Answer 2

Shield volcanoes are flat (low in height), broad base and summit, shield-like shape with gentle sloping sides.

Question 3

Stratovolcano viscosity, pressure, and explosiveness

Answer 3

High-silica lava has a high viscosity, which means gases are easily trapped, resulting in a build-up of pressure in the magma chamber. When magma rises towards the earth’s surface, gases expand, resulting in more explosive eruption, releasing large amounts of pyroclasts and ash clouds.

Question 4

Shield volcano viscosity, pressure, and explosiveness

Answer 4

Low siliva lava has low viscosity, means gases are not easily trapped. There is less pressure build-up in the volcano hence, eruptions are less explosive, releasing little gases, fast-flowing lava and small amounts of ashes.

Question 5

Stratovolcano viscosity, the spread of lava and base of the volcano

Answer 5

High-silica lava with high viscosity, Flows slower with much resistance, flows short distance, giving rise to narrow-based volcanoes.

Question 6

Shield volcano viscosity, the spread of lava and base of the volcano

Answer 6

Low-silica lava with low viscosity, Flows quickly due to less resistance, spread over a large distance, giving rise to broad-base volcanoes.

Question 7

Stratovolcano viscosity, cooling and gradient of the volcano

Answer 7

High-silica lava, accumulates as thick layers around the vent, cools and solidify quickly to form volcanoes with steep-sided slopes

Question 8

Shield volcano viscosity, cooling and gradient of the volcano

Answer 8

Low-silica lava spreads thin and wide, cools and solidify to form volcanoes with gentle sloping sides.

Question 9

Stratovolcano volcanic debris and height

Answer 9

Large amounts of ash accumulate to cause stratovolcano to increase in height as a tall cone-shape.

Question 10

Shield volcano volcanic debris and height

Answer 10

with each successive eruption, small amount of ash accumulate to cause shield volcanoes to increase in width rather than height, resulting in a flat dome-shape.

Question 11

Stratovolcano extras

Answer 11

• usually has a main pipe, secondary pipe, and cone
• major explosion can weaken the walls of the volcano and cause it to collapse inwards, resulting in the formation of the caldera
• commonly found at convergent plate boundaries

Question 12

Shield volcano extras

Answer 12

• Usually has a single main pipe

- commonly found at divergent plate boundaries

Question 13

Examples of stratovolcano

Answer 13

Mount. Pinatubo, Philippines ; Mount. Tambora, Indonesia

Question 14

Example of Shield volcano

Answer 14

Surtsey Island, Iceland; Kilauea, Hawaii