REVIEW FOR CHAPTER 6 – VOLCANOES

Where can we find volcanoes on earth?

Most volcanoes are found near subduction zones and mid-ocean ridges. This explains why the map of volcanoes on Earth matches

so well the map of tectonic plates. On the other hand, some volcanoes are located in remote places like in the middle of the Pacific plate (Hawaii), thousands of kilometres away from the

nearest plate boundary.

Before lava reaches the surface, the molten material is called?

magma

Main hazards from a quiet volcanic eruption is….Lava flow

Sometimes rising magma is blocked by horizontal layers of rock. The magma forces the layer of rock to bend upward into a landform called

Dome Mountain

Landforms From Lava and Ash• Composite Volcanoes have quiet eruptions

that alternate with explosive eruptions, forming layers of lava and ash.

Chapter 6 Volcanoes

Stages of Volcanic ActivityChapter 6 Volcanoes

• Extinct volcanoes are considered “dead” meaning that it is unlikely that they will erupt again

Stages of Volcanic ActivityChapter 6 Volcanoes

• Dormant volcanoes are considered “asleep” or “sleeping bears” meaning that they may become active in the future

Stages of Volcanic ActivityChapter 6 Volcanoes

• Active volcanoes are considered “live” meaning that it is erupting, or has shown signs that it may erupt in the near future

Magma Reaches Earth’s SurfaceChapter 6 Volcanoes

• Pyroclastic flow is an explosive eruption that includes hot gases, cinders (volcanic ash), and bombs (volcanic rocks).

Magma Reaches Earth’s SurfaceChapter 6 Volcanoes

• Aa is a very thick, slow moving lava. Aa contains high amounts of silica, which gives it it’s thickness. When aa hardens, it forms a rough surface consisting of jagged (sharp) lava chunks.

Magma Reaches Earth’s SurfaceChapter 6 Volcanoes

• Pahoehoe is a very thin, fast moving lava. Pahoehoe contains low amounts of silica, which gives it it’s thinness. When Pahoehoe hardens, it forms wrinkle and rope-like rock formations. Pahoehoe is hotter than Aa.

Magma Reaches Earth’s Surface• When a volcano

erupts, the force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent.

Chapter 6 Volcanoes

Landforms From Magma• Sills

Chapter 6 Volcanoes

Landforms From Magma• Dikes

Chapter 6 Volcanoes

Landforms From Magma• Volcanic Necks

Chapter 6 Volcanoes

Landforms From Magma• Batholiths

Chapter 6 Volcanoes

Landforms From Lava and Ash• Calderas are formed when a magma chamber is

emptied after an eruption and the volcano mountain collapses into the empty space creating a crater.

Chapter 6 Volcanoes

Crater Lake, Oregon

Landforms From Lava and Ash• Lava Plateaus are formed from runny lava

(pahoehoe) that cools in flat sheets of rock. Over time these layers form high plateaus.

Chapter 6 Volcanoes

Steamboat Rock, Washington

Landforms From Lava and Ash• Cinder Cone Volcanoes have explosive

eruptions of ash, cinders, and bombs that form a cone-shaped hill.

Chapter 6 Volcanoes

Mount Etna, Italy

Landforms From Lava and Ash• Shield Volcanoes have quiet eruptions and

have gentle slopes, which are not steep.

Chapter 6 Volcanoes