吉林大学：《地球科学概论》课程PPT教学课件（英文版）Chapter 5：Magma And Volcanoes

Chapter 5: Magma And Volcanoes

Chapter 5: Magma And Volcanoes

Introduction: Earth's Internal- Thermal Engine ■ Magma is molten rock beneath Earth’ s surface Because liquid magma is less dense than surrounding solid rock, and obviously more mobile, magma, once formed, rises toward the surface a Magma that reaches the surface does so by erupting through vents we call volcanoes

Introduction: Earth’s Internal-- Thermal Engine ◼ Magma is molten rock beneath Earth’s surface. ◼ Because liquid magma is less dense than surrounding solid rock, and obviously more mobile, magma, once formed, rises toward the surface. ◼ Magma that reaches the surface does so by erupting through vents we call volcanoes

Volcanoes a The term volcano comes from the name of the Roman god of fire, Vulcan There are different types of volcanoes. Eruption vary from gentle flows(Hawaii and Iceland) to catastrophic explosions(Mount St Helens, Mt Pinatubo, Soufriere Hills) The majority of eruption never make the news because they occur beneath the ocean, unobserved

Volcanoes ◼ The term volcano comes from the name of the Roman god of fire, Vulcan. ◼ There are different types of volcanoes. ◼ Eruption vary from gentle flows (Hawaii and Iceland) to catastrophic explosions (Mount St. Helens, Mt. Pinatubo, Soufriere Hills). ◼ The majority of eruption never make the news because they occur beneath the ocean, unobserved

Magma a Magma has a wide range of compositions, but silica(SiO2)always dominates the mix. Magma has high temperatures. Magma is fluid--it has the ability to flow a Most magma actually is a mixture of liquid (often referred to as melt) and solid mineral grains

Magma ◼ Magma has a wide range of compositions, but silica (SiO2) always dominates the mix. ◼ Magma has high temperatures. ◼ Magma is fluid—it has the ability to flow. ◼ Most magma actually is a mixture of liquid (often referred to as melt) and solid mineral grains

Composition of Magmas and Lavas The composition of magmas and lavas is controlled by the most abundant elements in the Earth-Si, Al, Fe, Ca, Mg, Na, K, H, and o. Three distinct types of magma are more common than others: Basaltic, containing about 50 percent SiO2 Andesitic, about 60 percent SiO2 Rhyolitic, about 70 percent Sio

Composition of Magmas and Lavas ◼ The composition of magmas and lavas is controlled by the most abundant elements in the Earth—Si, Al, Fe, Ca, Mg, Na, K, H, and O. ◼ Three distinct types of magma are more common than others: ◼ Basaltic, containing about 50 percent SiO2. ◼ Andesitic, about 60 percent SiO2. ◼ Rhyolitic, about 70 percent SiO2

Basaltic Andesitic Rhyolitic SiO SiO2 SiO 2 Al2O3MgO +Cao eo+ Fe203 LNa2O+K2O All other solid components The three main magmas

The three main Magmas

Basaltic magmas a Basaltic magmas are erupted by approximately 80 percent of volcanoes worldwide(the seafloor worldwide is mostly basalt) a Magma from Hawaiian volcanoes such as Kilauea and mauna loa is basaltic a The entire island of iceland is basaltic

Basaltic Magmas ◼ Basaltic magmas are erupted by approximately 80 percent of volcanoes worldwide (the seafloor worldwide is mostly basalt). ◼ Magma from Hawaiian volcanoes such as Kilauea and Mauna Loa is basaltic. ◼ The entire island of Iceland is basaltic

Andesitic and rhyolitic Magmas Andesitic magmas are about 10 percent of the total magma Magma from Mount St Helens in Washington State and Krakatau in Indonesia is usually andesitic. Rhyolitic magmas are about 10 percent of the total magma Magmas erupted from volcanoes that once were active at Yellowstone Park are mostly rhyolitic

Andesitic and Rhyolitic Magmas ◼ Andesitic magmas are about 10 percent of the total magma. ◼ Magma from Mount St. Helens in Washington State and Krakatau in Indonesia is usually andesitic. ◼ Rhyolitic magmas are about 10 percent of the total magma. ◼ Magmas erupted from volcanoes that once were active at Yellowstone Park are mostly rhyolitic

very viscous magma slow moving, from Kilauea olcano in Hawaii in 1989

Very viscous magma slow moving, from Kilauea Volcano in Hawaii in 1989

Fast flowing lava. low viscosity basaltic lava. Havaii in 1983

Fast flowing lava, low viscosity basaltic lava, Havaii in 1983