November 4, 2013 Agenda 1.Roll 2.PowerPoint: What Causes Volcanoes? 3.Possible Video Test is on Wednesday

Subject Area: What Causes Volcanoes? EQ: How does the heat from the Earth’s interior reach the surface? Questions: 1.How does magma form and move? 2.Where does magma form? 3.How does plate tectonics relate to volcanoes? 4.What methods do scientists use to predict volcanic eruptions?

What Causes Volcanoes? Scientists have studied volcanoes for years and understanding why a volcano forms is very difficult. There is no way to see deep into the Earth so they have to rely on models. There are many uncertainties about why a volcano will form.

The Formation of Magma Magma collects in pockets in the deeper regions in the Earth’s crust and in the uppermost layers of the mantle. This zone of magma is between 25 and 160 km below the surface. Partner Share: Where does magma form? Magma forms …

The Formation of Magma Mantle is hot and pliable; it is still considered to be a solid. The mantle is hot enough to melt any rock. The reason it doesn’t melt the crust is because of pressure. The pressure keeps the atoms tightly packed so the rock will not melt. Partner Share: 1.How does pressure determine whether mantle is solid or liquid? Pressure determines whether the mantle is solid or liquid by …

The Formation of Magma Rock will melt when the heat is increased and the pressure is decreased. The temperature of the mantle is fairly constant so the decrease of pressure will cause magma to form. Magma will sometimes melt solid rock or make its way through cracks and fissures. Partner Share: 1.What two factors may cause solid rock to become magma? The two factors are …

The Formation of Magma Once the magma is formed it will rise to the surface because it is less dense than the surrounding rock. Not all magma will come to the Earth’s surface. Some will cool and solidify while still in the Earth’s crust.

Where Volcanoes Form A large number of volcanoes lie directly on tectonic plate boundaries. The boundaries in the Pacific Ocean have many volcanoes this is called the Ring of Fire.

Where Volcanoes Form It is easier for magma to rise up through the crust where the plates collide or separate.

When Tectonic Plates Separate When tectonic plates separate a deep crack or rift will form. Decrease in pressure causes the mantle rock to partially melt and become magma.

When Tectonic Plates Separate Magma rises through the rift between the separating plates creating new crust. Most diverging plates are on the ocean floor.

When Tectonic Plates Collide In a subduction zone the oceanic crust will contain water which will lower the melting point in rock it comes in contact with. As it sinks deeper into the mantle it gets hotter and hotter.

When Tectonic Plates Collide The combination of increased pressure and heat will cause the water to be released. It then mixes with the mantle rock.

When Tectonic Plates Collide Heat from rising magma will cause some of the overlying continental crust to melt which is rich in silica.

This gooey thick silica rich magma is very likely to cause an explosive eruption. When Tectonic Plates Collide

Hot Spots Not all volcanoes are formed on a tectonic plate boundary. The volcanoes of Hawaii and several other places on Earth are called hot spots. Hot spots are places within tectonic plates that are directly above columns of rising magma.

Hot Spots The columns of hot rising magma are called magma plumes. Scientists are not sure what causes these plumes. Some think that a combination of heat and radioactivity keep the plumes rising. Partner Share: What is a Hot Spot? A Hot Spot is …

Predicting Volcanic Eruptions It is very difficult to predict when a volcano will erupt. Scientists will use the history of the volcano to classify them. The three classifications are extinct, dormant, and active.

Extinct Volcano Extinct Volcanoes are those that have not erupted in recorded history and probably never will.

Dormant Volcano Dormant Volcanoes are those that are not currently erupting but have erupted some time in recorded history.

Active Volcano Active Volcanoes are those that are in the process of erupting or show signs of erupting in the near future. Partner Share: 1.What are the three classifications for volcanoes? The three classifications are …

Predicting Volcanic Eruptions Dormant and active volcanoes keep scientists guessing. One sign they look for is, sometimes when a volcano is getting ready to erupt there will be a series of small earthquakes.

Predicting Volcanic Eruptions Scientists will look for bulges in the slope of a volcano. These bulges might be magma pushing against the inside of the volcano. Scientist will use a tiltmeter to detect small changes in the angle of the slope.

Predicting Volcanic Eruptions Scientists will also look for outflow of gases. As magma rises it will push gas out small holes in rock, when this happens the scientist know an eruption is not far away.

Predicting Volcanic Eruptions Scientist will also use satellite images that record radiation that can tell if magma is rising closer to the surface. Movie Partner Share: 1.Describe a technology scientists use to predict volcanic eruptions. The technology scientists use is …

Summary 1.Answer the essential question “How does the heat from the Earth’s interior reach the surface? 2.Your answer needs to be in complete sentences. 3.Place your answer at the bottom of the notes we did today. 4.Make sure you include the two factors that cause solid rock to become magma from your notes.

Earth Science Volcanoes Questions for your Science Notebook Earth Science Volcanoes What did you know? Skip 3 lines What did you learn? Skip 3 lines What do you want to know? Skip 3 lines