Presentation on theme: "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."— Presentation transcript:
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.subduction zones
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 Composite Volcanoes have quiet eruptions that alternate with explosive eruptions, forming layers of lava and ash. Chapter 6 Volcanoes
Stages of Volcanic Activity Chapter 6 Volcanoes Extinct Extinct volcanoes are considered “dead” meaning that it is unlikely that they will erupt again
Stages of Volcanic Activity Chapter 6 Volcanoes Dormant Dormant volcanoes are considered “asleep” or “sleeping bears” meaning that they may become active in the future
Stages of Volcanic Activity Chapter 6 Volcanoes Active 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 Surface Chapter 6 Volcanoes Pyroclastic flow Pyroclastic flow is an explosive eruption that includes hot gases, cinders (volcanic ash), and bombs (volcanic rocks).
Magma Reaches Earth’s Surface Chapter 6 Volcanoes Aa 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 Surface Chapter 6 Volcanoes Pahoehoe 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 magma chamber pipe vent 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 Sills Chapter 6 Volcanoes
Landforms From Magma Dikes Dikes Chapter 6 Volcanoes
Landforms From Magma Volcanic Necks Volcanic Necks Chapter 6 Volcanoes
Landforms From Magma Batholiths Batholiths Chapter 6 Volcanoes
Landforms From Lava and Ash Calderas 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 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 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 Shield Volcanoes have quiet eruptions and have gentle slopes, which are not steep. Chapter 6 Volcanoes