Chapter 18 Volcanic Activity
description
Transcript of Chapter 18 Volcanic Activity
![Page 1: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/1.jpg)
Chapter 18Volcanic Activity
![Page 2: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/2.jpg)
Section 18-1Magma
Objectives:• Describe factors that can affect the
formation of magma• Compare and contrast the different
types of magma
![Page 3: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/3.jpg)
Volcanic Eruptions
• In the last 10,000 years more than 1500 major volcanic eruptions have been recorded…where and why do these eruptions occur?
![Page 4: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/4.jpg)
How Magma Forms
• Recall that magma is a mixture of molten/melted rock, suspended mineral grains, and dissolved gasses found deep beneath the Earth’s surface.
![Page 5: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/5.jpg)
How Magma Forms
• Magma usually forms at temperatures between 800 and 1200 C (1600 to 2400 F)
• The temperature, and the pressure on the rock along with the amount of water in the rock all determine at what temperature the rock will melt.
![Page 6: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/6.jpg)
The Inner Earth1. Crust
(lithosphere)2. Upper Mantle3. Lower Mantle4. Outer Core5. Inner Core
![Page 7: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/7.jpg)
Rock Review
• Sedimentary (sediments) • Igneous (cooling magma/lava)• Metamorphic (heated solid rock)
![Page 8: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/8.jpg)
Pressure and Temperature
• As pressure increases on the rock inside the Earth, the temperature of the rock increases.
• So, the deeper down into the Earth that you go, the higher the temperature.
![Page 9: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/9.jpg)
Water and Magma
• If rock contains spaces that hold water, the rock will melt at a lower than normal temperature because the water found inside the rock helps it liquefy as it heats up.
![Page 10: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/10.jpg)
Types Of Magma
• Basaltic• Andesitic• Rhyolitic
![Page 11: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/11.jpg)
Basaltic Magma
• Typically forms when rocks in the upper mantle begin to melt, it tends to be fast moving and relatively quiet as it erupts due to its low gas content.
![Page 12: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/12.jpg)
Andesitic Magma
• Andesitic magma is made in subduction zones and is typically about 60% silica, it tends to move and erupt at a medium pace.
![Page 13: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/13.jpg)
Rhyolitic Magma
• Rhyolitic magma is thick and slow moving…it is filled with gas and water and tends to be very explosive because pressure builds within it.
![Page 14: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/14.jpg)
Viscosity• Viscosity refers to the rate or speed at which
something will flow.• If something has a high viscosity, the thicker
and slower it will flow• If something is said to have a low viscosity,
the thinner and faster it will flow.
![Page 15: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/15.jpg)
Section 18-2Intrusive Activity
Objectives:• Explain how magma affects overlying crustal
rocks• Compare and contrast intrusive igneous rock
bodies
![Page 16: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/16.jpg)
Density and Movement
• Because molten rock is nearly liquid compared to the solid rock around it, it is less dense and wants to move upward.
• What happens as the magma flows upward into cooler crust? The process is called “intrusion”.
![Page 17: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/17.jpg)
Magma Intrusions
![Page 18: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/18.jpg)
Intrusions
• The magma can force the solid rock to push apart and create fissures
• The magma can contact the upper solid rock and cause pieces of it to melt and fall into the magma pool
• The magma can immediately melt the rock into which it flows
![Page 19: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/19.jpg)
Plutons
As the flowing magma cools inside of the solid rock, it crystalizes and forms blocks, ribbons or
veins of new “intrusive” igneous rock.
![Page 20: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/20.jpg)
Batholiths
Batholiths are the specific name given largest formations of plutons. They are usually found in large mountain ranges. They cut across rock
layers.
![Page 21: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/21.jpg)
Laccoliths
Laccoliths tend to form near the Earth’s surface where they cause the rock above to push
upward in a dome shape.
![Page 22: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/22.jpg)
SillsSills are intrusions that form parallel to the existing rock, they tend to stay underground and flow like a “spill”.
![Page 23: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/23.jpg)
![Page 24: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/24.jpg)
Plate Movement
• Underground plutons can be brought to the surface as tectonic plates converge and push upward exposing the rock within it.
• Most igneous rock on the surface of the Earth is not from volcanic activity but from the slow gradual process of plate tectonics.
![Page 25: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/25.jpg)
![Page 26: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/26.jpg)
Section 18-3Volcanoes
Objectives:• Describe the major parts of a volcano• Compare and contrast shield, cinder-cone,
and composite volcanoes• Contrast the volcanism that occurs at plate
boundaries
![Page 27: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/27.jpg)
Anatomy of a Volcano
• The magma that erupts to the Earth’s surface is then called lava.
• The lava erupts through an opening in the crust called a vent.
• The lava will cool and solidify around the vent forming a mountain that is called a volcano.
![Page 28: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/28.jpg)
Anatomy of a Volcano
At the top of a volcano around the vent is a bowl-shaped depression called a crater
![Page 29: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/29.jpg)
Types of Volcanoes
• The appearance of a volcano depends on two factors:
1. The type of material that forms the volcano
2. The type of eruptions that occur
![Page 30: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/30.jpg)
Types of Volcanoes
• Shield• Cinder-cone• Composite
![Page 31: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/31.jpg)
Shield Volcanoes
• A wide volcano/mountain with gently sloping sides and a nearly circular base
• It results from the slow eruption of basaltic lava that builds up in layers
• Hawaiian Islands
![Page 32: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/32.jpg)
Shield Volcano
![Page 33: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/33.jpg)
Cinder-Cone Volcanoes
• Very steep mountain/volcano that results from material being ejected straight up into the air and falling back down around the vent
• Magma/lava contains some gases that make the eruptions explosive
![Page 34: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/34.jpg)
Cinder Cone
![Page 35: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/35.jpg)
Composite Volcanoes
• Larger versions of cinder-cone that have been made of layers of lava and solid material. The magma/lava that makes them up is full of gas that builds up until it finally explodes violently.
• Mt. St. Helens
![Page 36: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/36.jpg)
Composite
![Page 37: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/37.jpg)
Volcanic Material
Rock fragments thrown into the air during an eruption are called tephra.
• Classified by size– Dust– Ash– Lapilli– Volcanic blocks (angular)– Volcanic bombs (rounded)
![Page 38: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/38.jpg)
Pyroclastic Flows
• Violent eruptions that send out a wave of gas, ash, and tephra that can travel up to 400 mph.
![Page 39: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/39.jpg)
Where do Volcanoes Occur?
The distribution of volcanoes around the world is not random, most occur at plate boundaries.• 80% convergent• 15% divergent• 5% non-boundary “Hot Spots”
![Page 40: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/40.jpg)
Convergent Volcanism
Plates coming together, this forms the Pacific Ocean “Ring of Fire” and the “Mediterranean
Ring” in the Atlantic.
![Page 41: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/41.jpg)
Divergent Volcanism
• Plates spreading apart also create a way for magma to escape…these are called rift zones.
• Mid-Atlantic Ridge
![Page 42: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/42.jpg)
Hot Spots
• The Hawaiian Islands are not formed along a plate boundary but instead are found in an area of the mantle that is usually hot called a “hot-spot”
• As the plates move over the hot spot volcanoes form.
![Page 43: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/43.jpg)
![Page 44: Chapter 18 Volcanic Activity](https://reader035.fdocuments.in/reader035/viewer/2022062502/56816592550346895dd85e46/html5/thumbnails/44.jpg)