Volcanoes Lecture PDF

Volcanoes (and a Little Review) 1 Volcano: Another Word Word VOLCANO is derived from VULCANO, the name of a volcanic Italian island, north of Sicily. The island itself is named after VULCAN, the ancient Roman god of fire! VULCANO, Italy...

Volcanoes (and a Little Review) 1 Volcano: Another Word Word VOLCANO is derived from VULCANO, the name of a volcanic Italian island, north of Sicily. The island itself is named after VULCAN, the ancient Roman god of fire! VULCANO, Italy Statue of Vulcan by Danish and Icelandic sculptor Albert B. Thorvaldsen (1770 – 1844) 2 Volcano: In Native Legend Mount Saint Helens is a volcano in Washington State. It continuously erupted from 2004 – 2008 and in 1980 caused most disastrous eruption in US history. YAKAMA Nation of Washington State (northwest USA) referred to Mount Saint Helens as Si Yett (Si Yett = woman) According to legend, Mount Saint Helens was a beautiful maiden placed on Earth to protect the bridge of the gods on the Columbia River from two battling brothers. The battling brothers were Mount Adams and Mount Hood, two other volcanoes in the area, considered potentially active and dormant, respectively! Read more about volcano legends here! https://www.discovermthood.com/legend-of-three-mountains/ https://volcano.oregonstate.edu/native-american-myths YAKAMA fishers on the Columbia River. 3 A Journey to the Center of the Earth In simplest terms, a VOLCANO is an opening on the surface of the Earth. CRUST To understand Earthly volcanoes let us briefly review Earth’s 3 layers: MANTLE the CORE (INNER CORE and OUTER CORE) the MANTLE OUTER CORE the CRUST INNER CORE OUTER CORE consists of MOLTEN ROCK but INNER CORE contains SOLID ROCK due to high pressures. 4  A Journey to the Center of the Earth In simplest terms, a VOLCANO is an opening on the surface of the Earth. To understand Earthly volcanoes let us briefly review Earth’s 3 layers: CRUST the CORE (INNER CORE and OUTER CORE) MANTLE the MANTLE OUTER the CRUST CORE While MANTLE and CRUST are mostly SOLID ROCK, varying temperatures and pressures can result in presence of MOLTEN INNER ROCK in lower portions of CRUST and MANTLE. CORE This MOLTEN ROCK (or MAGMA) can escape onto Earth’s CRUST through volcanoes. 5 Magma: Travelling Rock In simplest terms, a volcano is an opening on the surface of the Earth. Volcanoes allow molten or semi-molten rock known as MAGMA to rise up from the lower portions of earth’s CRUST and the upper portions of the MANTLE and erupt/escape onto earth’s surface. MAGMA consists of: ✓ Liquified rocks (known as the MELT) ✓ Crystallized minerals ✓ Solid rocks (that are pulled into the MELT) ✓ Dissolved gases (including water vapour) 6 Thinking Question? Are MAGMA and LAVA the same thing? Oldest known depiction of a volcanic eruption? Art from Chauvet-Pont D’Arc cave, France 7 Thinking Question? Are MAGMA and LAVA the same thing? Absolutely not! MAGMA LAVA MAGMA is molten or semi-molten LAVA is molten or semi-molten rock rock BENEATH Earth’s surface. ON Earth’s surface (the MAGMA once it has erupted from the volcano). Along with the rock, it may also contain suspended mineral Along with the rock, it may also crystals and gases. contains other suspended minerals. Temp: 600oC – 1300oC Temp: 700oC – 1200oC 8 A Journey to the Center of the Earth In simplest terms, a volcano is an opening on the surface of the Earth. Quick Review: the CORE (INNER CORE and OUTER CORE) the MANTLE the CRUST Image to right also indicates thickness for each component. Sum of these thicknesses = Earth’s radius ≈ 6370 km. Earth’s diameter is 2 x 6370 km ≈ 12740 km! 9 A Journey to the Center of the Earth In simplest terms, a volcano is an opening on the surface of the Earth. Also worth noting: The OCEAN CRUST (aka OCEANIC CRUST) is thinner but denser than the CONTINENTAL CRUST. Often we couple upper portions of the MANTLE and the CRUST and refer to these as the LITHOSPHERE. LITHOSPHERE: The outermost layers of Earth; namely the upper portion of the MANTLE + the CRUST. 10 Review Question? The LITHOSPHERE is one of the “4 SPHERES OF THE EARTH. Who are the other 3 spheres? 11 Review Question? The LITHOSPHERE is one of the “4 SPHERES OF THE EARTH. Who are the other 3 spheres? LITHOSPHERE (aka ATMOSPHERE: The GEOSPHERE): The GASES surrounding our outermost layers of Earth; planet and held in place by namely the upper portion Earth’s GRAVITY. Most of the MANTLE + the gases are close to Earth’s CRUST. surface in the lowest region of the ATMOSPHERE called the TROPOSPHERE. HYDROSPHERE: All WATER on or near Earth’s surface (e.g., oceans, BIOSPHERE: All LIVING lakes, rivers, groundwater ORGANISMS on Earth aquifers, even water (mammals, birds, fish, vapour in the atmosphere) reptiles/amphibians, plants, fungi, bacteria, etc...). 12 LITHOSPHERE: The Shape Shifter Earth’s entire CRUST and UPPER MANTLE (i.e., the LITHOSPHERE) can be subdivided into large rocky plates known as TECTONIC PLATES. PLATE TECTONICS: A theory by which TECTONIC PLATES and their movements are employed to explain landforms (e.g., mountain building - formation of trenches/ridges), earthquakes and VOLCANOES. The LITHOSPHERE is divided into 7 MAJOR TECTONIC PLATES and 8 MINOR TECTONIC PLATES. 13 LITHOSPHERE: The Shape Shifter LITHOSPHERE and therefore TECTONIC PLATES it is made of, sits on the ASTHENOSPHERE. ASTHENOSPHERE: partially molten layer of MANTLE. ASTHENOSPHERE moves due to heat transfer and rise and fall of partially molten rocks within it. When ASTHENOSPHERE below moves, TECTONIC PLATES are dragged along and move too! 14 LITHOSPHERE: The Shape Shifter Due to ASTHENOSPHERE movement, TECTONIC PLATES can: ✓ pull away from one another (i.e., split) ✓ collide into one another ✓ slide along one another Pulling away (or splitting) TECTONIC PLATES are said to form a DIVERGENT PLATE BOUNDARY. Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. TECTONIC PLATES that slide along one another are said to form a TRANSFORM PLATE BOUNDARY. 15 LITHOSPHERE: The Shape Shifter Depending on where the PLATE BOUNDARY lies, it can have different THICKNESSES and DENSITIES. Remember: DENSITY = MASS ÷ VOLUME. Oil floats of water as it has a lower density. As mentioned in comparing OCEAN CRUST and CONTINENTAL CRUST: if TECTONIC PLATE is under OCEAN CRUST then it will be DENSER and THINNER. if TECTONIC PLATE is under land (i.e., CONTINENTAL CRUST), then it will be LESS DENSE and THICKER. Upon collision (at CONVERGENT PLATE BOUNDARIES), DENSER TECTONIC PLATE will slide under a LESS DENSE PLATE. Thus, a plate carrying OCEAN CRUST will sink under a plate carrying CONTINENTAL CRUST. 16 LITHOSPHERE: The Shape Shifter DIVERGENT PLATE BOUNDARY: Pulling away (or splitting) TECTONIC PLATES are said to form a DIVERGENT PLATE BOUNDARY. DIVERGENT PLATES are especially encountered under ocean floors. Volcanic activity and earthquakes (to be examined later on) are often encountered along DIVERGENT PLATES, particularly along the mid-ocean RIDGES. RIDGE: A long, narrow, raised part of Earth’s surface (e.g., long, narrow mountain chains). The sides of the RIDGE slope away from the narrow top known as a CREST. 17 LITHOSPHERE: The Shape Shifter DIVERGENT PLATE BOUNDARY: DIVERGENT PLATES such as those found under the mid-Atlantic result in the formation of RIDGES. Volcanic activity and earthquakes (to be examined later on) are often encountered along DIVERGENT PLATES. Here we see MAGMA rising up along a mid- ocean RIDGE 18 LITHOSPHERE: The Shape Shifter DIVERGENT PLATE BOUNDARY: DIVERGENT PLATES such as those found under the mid-Atlantic result in volcanic activity (the release of MAGMA onto Earth’s surface and thus the formation of RIDGES. In fact, 70% of volcanic activity occurs under water, along mid- oceanic RIDGES! These mid-oceanic RIDGES measure 60,000 km in total and are all linked together. They can be viewed as one entity/one continual volcano! 19 LITHOSPHERE: The Shape Shifter DIVERGENT PLATE BOUNDARY: DIVERGENT PLATES such as those found under the mid-Atlantic result in THE MID-OCEANIC volcanic activity (the release of RIDGE (in RED) MAGMA onto Earth’s surface and thus the formation of RIDGES. In fact, 70% of volcanic activity occurs under water, along mid- oceanic RIDGES! These mid-oceanic RIDGES measure 60,000 km in total and are all linked together. They can be viewed as one entity (THE MID-OCEANIC RIDGE) and therefore one continual volcano! 20 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. Whenever a plate carrying OCEAN CRUST collides with a plate carrying CONTINENTAL CRUST, the OCEAN CRUST (and plate) sinks below the CONTINENTAL CRUST (and plate) due to its greater density. The sinking of one TECTONIC PLATE beneath another creates what is known as a SUBDUCTION ZONE. 21 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. The sinking of one TECTONIC PLATE beneath another creates what is known as a SUBDUCTION ZONE. SUBDUCTION ZONE: OCEAN CRUST sinking beneath CONTINENTAL CRUST. 22 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. The sinking of one TECTONIC PLATE beneath another creates what is known as a SUBDUCTION ZONE. CONVERGENT PLATE BOUNDARIES can to be seen in RED (see image). They are home to many (MANY) of the world’s most famous volcanoes and lots of earthquake activity. 23 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. The sinking of one TECTONIC PLATE beneath another creates what is known as a SUBDUCTION ZONE. The sinking of one plate drags tonnes of sediment into the molten MAGMA below. This alters the MAGMA and results in a thick MAGMA rich in SILICA (silicon dioxide). FUN FACT: Sand = silicon dioxide (SiO2), aka quartz. 24 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. The sinking of one TECTONIC PLATE beneath another creates what is known as a SUBDUCTION ZONE. Thick, gummy magma of volcanoes along SUBDUCTION ZONES does not flow as easily once it erupts as LAVA (releasing lots of gases in the process – mainly H2O, CO2, SO2). Since the LAVA does not flow away so easily, we get a tall, cone-shaped volcano known as a STRATOVOLCANO. 25 LITHOSPHERE: The Shape Shifter CONVERGENT PLATE BOUNDARY: Colliding TECTONIC PLATES are said to form a CONVERGENT PLATE BOUNDARY. FAMOUS STRATOVOLCANOES: MOUNT SAINT HELENS (USA) MOUNT VESUVIUS (ITALY) MAYON (THE PHILIPPINES) 26 LITHOSPHERE: The Shape Shifter TRANSFORM PLATE BOUNDARY: TECTONIC PLATES that slide along one another are said to form a TRANSFORM PLATE BOUNDARY. The rubbing of two plates at TRANSFORM PLATE BOUNDARIES can often result in earthquakes due to built up stress caused when plates get stuck and subsequently manage to slide by one another. e.g., at the SAN ANDREAS FAULT along the Western USA. 27 Thank you for listening! Mount Fuji, Japan. An ACTIVE stratovolcano! 28