Geologic Time Scale PDF

Geologic Time Scale 1 Geologic Time Scale: Fossil Facts Last class we encountered three types of fossils: TRACE FOSSILS: FOSSILS depicting organism behavior including: footprints, coprolites (fossilized dung),...

Geologic Time Scale 1 Geologic Time Scale: Fossil Facts Last class we encountered three types of fossils: TRACE FOSSILS: FOSSILS depicting organism behavior including: footprints, coprolites (fossilized dung), TRACE FOSSIL: Here we fossilized nests/burrows. observe burrows produced by aquatic crustaceans. MOLD FOSSIL: form when organism gradually dissolves away, leaving behind impression of body, leaves, flowers, etc… CAST FOSSIL: Same process (organism gradually dissolves away) but impression/MOLD left behind filled with sediment that ultimately forms rock, replacing original organism. To wrap this topic up, let’s also discuss: MOLD FOSSIL: CAST FOSSIL: Here PETRIFIED FOSSILS Here we observe a we observe another TRILOBITE. TRILOBITE. PRESERVED REMAINS 2 Geologic Time Scale: Fossil Facts PETRIFIED FOSSILS: Remember the piece of petrified wood we saw in class? How did it form? Firstly, let’s look at the word itself. PETRA = Latin for rock or stone PETRIFIED wood seen here in Petrified PETRIFIED = turned to stone/PETRIFICATION = to turn to Forest National Park, Arizona. stone! PETRIFICATION occurs when buried remains (e.g., WOOD) are exposed to (ground)water rich in molecules/IONS that make up MINERALS (e.g., CaCO3, SiO2). MINERALS gradually deposit and in so doing, gradually replace original organic matter found in ORGANISM’S remains. PETRIFIED wood log. Can see the REMEMBER – plants are ORGANISMS too! growth rings in these prehistoric trees. 3 Geologic Time Scale: Fossil Facts PETRIFIED FOSSILS: ORGANISM: an individual animal, plant or single-celled life form. When dealing with PETRIFICATION/PETRIFIED FOSSILS, notice that MINERALS are NOT filling an empty space left behind after an organism decays (as occurs when form CAST PETRIFIED log seen here in Petrified FOSSILS). Forest National Park, Arizona. Instead, MINERALS are GRADUALLY replacing ORGANIC MATTER. Ultimately, can view PETRIFICATION as process by which remains of an ORGANISM gradually turn to stone! According to Norwegian legend, trolls only go out at night as first rays of sunlight would turn them to stone (i.e., PETRIFY them). 4 Geologic Time Scale: Preserved Remains PRESERVED REMAINS: Last class we discussed how BOG BODIES can be preserved for thousands of years. Unlike with FOSSILS, here organism’s original organic matter (i.e., bones and soft tissue) is preserved/kept/left behind. RESIN dripping from a pine tree Another way for an ORGANISM’S remains to be preserved (traditionally used for medicinal is within AMBER! purposes). AMBER itself is fossilized tree RESIN. RESIN: a substance flowing beneath tree bark to protect in case of insects, disease or physical damage (e.g., breaks, cracks). RESIN covers breaks, cracks, injuries and hardens to form a seal/barrier. Cherry tree RESIN. 5 Geologic Time Scale: Preserved Remains PRESERVED REMAINS: Some of the RESIN from trees may reach forest floor. Since RESIN is sticky, it can entrap and subsequently engulf creatures (insects, arachnids, amphibians) and plant bits within! Eventually RESIN is compressed by layers of sediment that Tiny amphibians trapped in AMBER! form above it. Overtime, chemical compounds within RESIN transform to form AMBER! We can often observe organism’s PRESERVED REMAINS within the amber. Earth’s largest known deposits of AMBER are in Europe’s Baltic Region. This AMBER is referred to as Baltic AMBER. Majority of AMBER comes from Kaliningrad Oblast, Russia. Europe’s Baltic Region and Baltic Amber. 6 Tangent: The Amber Room Once referred to as the 8th wonder of the world, the AMBER ROOM remains a mystery to this day. Although it moved around and grew with renovations, it ultimately found itself in the Catherine Palace, Pushkin Russia (south of Saint Petersburg). Final version/renovated AMBER ROOM covered 180 square feet and contained 6 tons (6000 kg) of AMBER and other semi- The AMBER ROOM! precious stones. During World War 2 (WW2), advancing Nazi forces tore down AMBER ROOM and placed it in a castle museum in Königsberg, Germany on Baltic Coast. Fearing Allied advance and bombing, AMBER ROOM dismantled again. A 1944 Allied bombing raid on Königsberg turned museum to Catherine Palace, Russia. rubble. Rest is a mystery… 7 Tangent: The Amber Room Theories: crates containing AMBER ROOM destroyed during bombing. AMBER room crates remain hidden somewhere in Königsberg (which is now Kaliningrad). AMBER ROOM crates are at bottom of Baltic Sea as ship transporting it away sunk. NOTE: In 1997, one panel of AMBER ROOM recovered in Bremen, Germany when son of dead German soldier tried to sell it, not knowing what it was. The AMBER ROOM! 8 Geologic Time Scale: Finally… Once more, given that specific FOSSILS only found in SPECIFIC ROCK LAYERS: finding specific FOSSILS in rock layer tells geologists how old rock is in relation to other rocks in area. FOSSIL RECORD: history of Earth as documented by FOSSILS. different periods of GEOLOGIC TIME /different layers of rock have different animal/plant/bacteria/fungi FOSSILS. Returning to GEOLOGIC TIME SCALE: GEOLOGIC TIME SCALE divided into (in order from longest to shortest subdivision): EONS: longest subdivision/amount of time ERAS: next longest subdivision/amount of time FOSSIL RECORD is history of Earth as PERIODS: shorter subdivision/amount of time documented by FOSSILS. EPOCHS: shortest subdivision/amount of time 9 Geologic Time Scale A 2nd representation of GEOLOGIC TIME SCALE I really like – also includes the 5 MASS EXTINCTIONS, times when much of life on Earth, well, died.. 5 MASS EXTINCTIONS: NOTE: mya = million years ago. ORDOVICIAN-SILURIAN: 440 mya DEVONIAN: 365 mya PERMIAN-TRIASSIC: 250 mya TRIASSIC-JURASSIC: 210 mya CRETACEOUS-TERTIARY: 65 mya https://geologyscience.com/geology- branches/paleontology/geologic-time-scale/ 10 Geologic Time Scale: Finally… EONS: longest subdivision in GEOLOGIC TIME SCALE. There have only been 4 EONS since formation of our planet! HADEAN: 4.6 billion to 4.0 billion years ago. Earth is forming during this time. No life – Earth way too hot and molten! Remember formation of MOON? When ARCHEAN: 4.0 billion to 2.5 billion years ago. Earth’s CRUST Earth and THEIA collided? This occurred cooling down enough to allow for life to begin! during HADEAN EON! PROTEROZOIC: 2.5 billion to 541 million years ago. Life forms encountered include bacteria, algae, jellyfish! The “PRECAMBRIAN” is a term often used to refer to HADEAN, ARCHEAN and PROTEROZOIC EONS combined. Final EON, which we are still in today, is PHANEROZOIC (it started 541 million years ago). Remember the STROMATOLITES/ CYANOBACTERIA MOUNDS, oldest fossils PHANEROZOIC EON divided into ERAS, PERIODS, EPOCHS known? These date back to ARCHEAN EON! 11 Thank you for listening! RIP DODO BIRD. Last seen in 1662. We are currently in HOLOCENE/ANTHROPOCENE extinction. It is still going… inspiration for Geology’s 2024 SPACEweek display entitled “Who Next”. If anyone asks you, we are currently in the: PHANEROZOIC EON, CENOZOIC ERA, QUATERNARY PERIOD, HOLOCENE EPOCH!!! 12 Geologic Time Scale 1 Geologic Time Scale: Remember Me? 2 Geologic Time Scale: I’m back! Now let’s take a closer look! 3 Geologic Time Scale: Overview As previously mentioned, GEOLOGIC TIME SCALE: a calendar of events in Earth’s history a representation of time based on Earth’s GEOLOGIC RECORD/ROCK LAYERS a tool breaking up/dividing history/time into usable, understandable segments/intervals Within GEOLOGIC TIME SCALE, GEOLOGISTS divide history/time into EONS, ERAS, PERIODS and EPOCHS. Segments/intervals within GEOLOGIC TIME SCALE have been named and dated based on research carried out over more than a century. Upon closer examination, one could also say GEOLOGIC TIME SCALE: divides up history of Earth based on life-forms that existed during specific times. How do we know about these life-forms given that they can go back billions of years? 4 Geologic Time Scale: Fossils How do we know about these life-forms given that they can go back billions of years? ANSWER: FOSSILS. FOSSILS essential to our understanding of GEOLOGIC TIME SCALE. Let’s take a closer look. FOSSILS: FOSSIL of a pterosaur, Pterodactylus remains (e.g., shells, skeletons) or traces (e.g., worm burrows, kochi, in LIMESTONE (Germany) footprints) of an organism from past preserved in sediment or rock geologically altered remains of a once-living organism and/or its behaviour PALEONTOLOGY: study of FOSSILS from 3 Greek words, PALEO, ONTO and LOGY! FOSSILS essential to understanding PALEO = ancient, ONTO = being, LOGY = study. GEOLOGIC TIME SCALE PALEONTOLOGY = ancient being study! PALEONTOLOGY = scientist who studies fossils. 5 Geologic Time Scale: Fossil Record With help of FOSSILS, geologists can determine: age of a rock relative to other rocks environment in which rock formed FOSSIL RECORD: history of Earth as documented by FOSSILS. different periods of GEOLOGIC TIME /different layers of rock have different animal/plant/bacteria/fungi FOSSILS in observing layers of rock, find that species appear, go extinct (i.e., disappear) evolve and change environments Given that specific FOSSILS only found in SPECIFIC ROCK LAYERS: finding specific FOSSILS in rock layer tells geologists how old rock is in relation to other rocks in area finding specific FOSSILS also enables geologists to match FOSSIL RECORD is history of Earth as age of rock in one area to another area and even across documented by FOSSILS. continents if organism had large enough range 6 Geologic Time Scale: Fossil Record BIOSTRATIGRAPHY: use of FOSSILS to (help) determine age of rocks. FOSSILISATION (i.e., process of becoming a FOSSIL) is “destructive”. While all living things (e.g., plant, animal, bacteria, fungus) can become a FOSSIL, most do not! Remains are more often eaten/consumed or destroyed. Some parts of organisms (e.g., bones, teeth, shells) more likely preserved than others (e.g., flesh, organs). Why? These harder parts more resistant to destruction/decomposition over the years and less likely to be eaten. FOSSIL RECORD is history of Earth as documented by FOSSILS. Jellyfish – don’t have harder parts and rare in FOSSIL RECORD. 7 Geologic Time Scale: Fossil Facts TRACE FOSSILS: FOSSILS depicting organism behavior including: footprints, coprolites (fossilized dung), fossilized nests/burrows. To be considered a FOSSIL, must have a BIOGENIC origin. TRACE FOSSIL: Tyrannosaur BIOGENIC = made by/from living organisms. footprint (B.C, Canada). Often, oldest FOSSILS difficult to confirm as BIOGENIC since: no longer a trace of original biological material organisms may not resemble what we can easily recognize. Oldest known fossils: CYANOBACTERIA from rocks of Western Australia dated to 3.5 billion years ago NOTE: oldest rocks only a little older (3.8 billion years old) FOSSILIZED CYANOBACTERIA what we observe is STROMATOLITES are oldest known FOSSILS and can date back to 3.5 billion years ago. 8 Geologic Time Scale: Stromatolites – Living Fossils STROMATOLITES: layered SEDIMENTARY formations created by PHOTOSYNTHETIC (make their own food) microorganisms (organisms you can only see with a MICROSCOPE) such as CYANOBACTERIA. layers of PHOTOSYNTHETIC microorganisms (e.g., CYANOBACTERIA) which formed layers and ultimately MOUNDS over time. Living STROMATOLITE MOUNDS in Shark Bay, Australia are believed to be among oldest living Living STROMATOLITE MOUNDS still found today in organisms on Earth (these about 2 billion years old). marine environments! Way to go CYANOBACTERIA! MOUNDS usually no more than half a meter tall. We’ve seen the oldest FOSSILS. Now, how do most FOSSILS form? STROMATOLITE FOSSIL 9 Geologic Time Scale: Fossil Formation Two important definitions. AEROBIC: any environment or situation/condition where free oxygen (O2) is present AEROBIC organisms are organisms that require oxygen to survive. ANAEROBIC: any environment or situation/condition where “free oxygen” (O2) absent. 2400 year old BOG body. BOG bodies such as this person found in a Danish bog very well preserved due to lack of NOTE: may contain oxygen bound to other atoms free oxygen, cold temperatures and acidic water (all of such as in nitrate (NO3-), nitrite (NO2-) or sulfite which prevent decomposition) in BOG. (SO32-) but cannot find free oxygen (O2). BOG BODIES can be preserved thousands of years. Such conditions found in deep soils, deep sea but closer to home, ANAEROBIC soils can also be BOG: a wetland/wet spongy ground that accumulates found in wetlands, swamps, bogs, etc… PEAT due to deposit of dead plant materials, often mosses. 10 Geologic Time Scale: Fossil Formation How do fossils form? Firstly, organism must die (Nobel Prize statement)! Predators/scavengers do not consume it or a least part of it. Remains find themselves buried quickly, in soft sediments, to avoid being eaten, and rapid decay Ideally remains buried in low free oxygen or ANAEROBIC conditions (e.g., bogs, wetlands, Example of the formation of a FOSSIL! swamps, deep ocean, deep lake, under volcanic ash). Must be buried for thousands or millions of years. FOSSILIZED gorgosaurus, As layers of sediment/pile up on top of remains, rocks Redpath Museum, form around the organism through LITHIFICATION McGill University (COMPACTION and CEMENTATION). 11 Geologic Time Scale: Fossil Formation How do fossils form? Rocks forming around organism change shape and composition of remains! Empty spaces within body/organism can be filled with sediment (eventually becoming rock) or can be filled with minerals (deposited by groundwater). Sometimes, organism itself completely dissolves leaving Velociraptor FOSSIL demonstrating MOLD surrounded by rock! famous dinosaur had feathers! At this point can form one of two fossil types: MOLD FOSSILS CAST FOSSILS. Velociraptor looks a bit like my chickens! 12 Geologic Time Scale: Fossil Formation How do fossils form? MOLD FOSSIL: form when organism gradually dissolves away, leaving behind impression of body, leaves, flowers, etc… CAST FOSSIL: Same process (organism gradually dissolves away) but impression/MOLD left behind filled with sediment that ultimately forms rock, replacing original organism. Finally, rocks around fossil WEATHERED/ERODED away, allowing us to discover these special and informative remains! Okay – now back to GEOLOGIC TIME SCALE! MOLD FOSSIL (left) vs CAST FOSSIL (right)! 13 Thank you for listening! Dueling fossils!!! Go stegosaurus!!! Run! 14 Geology (what’s it all about) 1 Geology: What’s it all About GEOLOGY: branch of science dealing with Earth (our planet) More specifically, GEOLOGY deals with Earth’s: rocky body 4.55 billion year history environmental changes Comes from the Greek words: GEO = Earth LOGOS = discourse GEOLOGIST: an Earth scientist (i.e., geoscientist) John William Dawson, Geologist 2 Geology: What’s it all About GEOLOGY: branch of science dealing with Earth (our planet) GEOLOGISTS: ✓ examine, characterize and classify Earth’s materials ✓ study Earth’s processes of change ✓ identify key relationships of cause (process) and effect (product) ✓ design, develop and test models explaining processes/observation’s ✓ publish inferences about Earth and how it functions NOTE: INFERENCE = conclusions based on evidence/reasoning John William Dawson, Geologist 3 Geology: What’s it all About GEOLOGY: branch of science dealing with Earth (our planet) GEOLOGISTS (and all scientists) can make two types of observations/gather two types of information. Namely, they can gather QUALITATIVE INFORMATION and QUANTITATIVE INFORMATION. QUALITATIVE INFORMATION: Information describing how something looks, feels, smells, sounds, tastes, behaves. Colline d’Outremont, Montreal Information that does not have a specific numerical value and units. e.g., Mount Royal has a higher elevation than the surrounding areas. 4 Geology: What’s it all About GEOLOGY: branch of science dealing with Earth (our planet) GEOLOGISTS (and all scientists) can make two types of observations/gather two types of information. Namely, they can gather QUALITATIVE INFORMATION and QUANTITATIVE INFORMATION. QUANTITATIVE INFORMATION: Information that can be measured using various tools. Colline d’Outremont, Montreal Information that has specific numerical values and units. e.g., The Mount Royal has 3 peaks, Colline de la Croix (233 meters), Colline d’Outremont (211 meters) and Westmount Summit (201 meters) For Colline d’Outremont, 211 is the numerical value and meters is UNIT. 5 Geologic Record: Like an Open Book GEOLOGIC RECORD: history of Earth as recorded in the rocks/rock layers that make up its crust. Earth is covered with millions of rock layers. Each of the layers is equivalent to a page in Earth’s history book/GEOLOGIC RECORD. Individual layers correspond to specific times and events. Layers can range from millimeters to meters in thickness. Rock layers clearly visible on the Mount Royal Layers have distinguishing features ranging from sand grains/microscopic fossils to fossilized trees, dinosaurs and even ancient riverbeds. BOTTOM layer is the OLDEST, whereas TOP layer is the YOUNGEST. 6 Spatial Scales of Obervation: Zoom in, Zoom out. GEOLOGISTS examine all of Earth’s materials but do so at GLOBAL LEVEL different SPATIAL SCALES OF OBSERVATION. SPATIAL SCALES OF OBSERVATION are the different levels at which we can make observations. Imagine zooming in and zooming out when taking a picture. ATOMIC Observations can be made at GLOBAL level (i.e., we LEVEL consider entire planet Earth within Universe) all the down to ATOMIC level (i.e., examine arrangement of atoms and NOTE: ions are molecules in substances). atoms that have gained or lost electrons SPATIAL SCALE OF OBSERVATION selected depends on what it is we are trying to examine/understand. SPATIAL SCALE OF OBSERVATION Let us consider the different SPATIAL SCALES OF selected depends on what it is we are trying to OBSERVATION we can employ and their corresponding examine/understand. UNITS. 7 Spatial Scales of Obervation: Zoom in, Zoom out. SPATIAL SCALES OF OBSERVATION MACROSCOPIC/ SCALE OF OBSERVATION USED TO EXAMINE UNITS MICROSCOPIC Entire planet/planet within GLOBAL Thousands of kilometers (km) universe Portions of oceans, continents, REGIONAL countries, provinces, states, kilometers (km) MACROSCOPIC islands,… (visible to naked eye) Specific locations that can be LOCAL (FIELD SITE) meters (m) pinpointed on a map Sample of a mineral, rock, air, HAND SAMPLE centimeters (cm) or water, oganism, that can be held (FIELD/LAB SAMPLE) millimeters (mm) in your hand Features of a HAND SAMPLE that millimeters (mm) or MICROSCOPIC can only be seen with a MICROSCOPIC micrometers (µm) magnifying glass or microscope (invisible to naked eye) Arrangement of atoms, ions or ATOMIC/MOLECULAR nanometers (nm) molecules in a substance 8 Spatial Scales of Obervation: Zoom in, Zoom out. GEOLOGISTS examine all of Earth’s materials but do so at different SPATIAL SCALES OF OBSERVATION. SPATIAL SCALE OF OBSERVATION selected depends on what it is we are trying to examine/understand. Very quickly, please note that: 1 kilometer (km) = 1000 meters 1 meter (m) = 100 centimeters (cm) 1 centimeter (cm) = 0.01 meters (m) 1 millimeter (mm) = 0.001 meters (m) 1 micrometer (µm) = 0.000001 meters (m) 1 nanometer (nm) = 0.000000001 meters (nm) 9 Geologic Time Scale: It’s About to get Real. GEOLOGIC TIME SCALE: a calendar of events in Earth’s history a representation of time based on Earth’s GEOLOGIC RECORD/ROCK LAYERS a tool breaking up/dividing history/time into usable, understandable segments/intervals Within GEOLOGIC TIME SCALE, GEOLOGISTS divide history/time into EONS, ERAS, PERIODS and EPOCHS. Segments/intervals within GEOLOGIC TIME SCALE have been named and dated based on research carried out over more than a century. What exactly does this GEOLOGIC TIME SCALE look like? 3, 2, 1… 10 Geologic Time Scale: It Just got Real. 11 Geologic Time Scale: It Just Got Real. 12 Thank you for listening! Reminder of an abandoned ski hill, Colline d’Outremont again! 13 Volcanoes (and the rocks they produce) 1 REVIEW: Previous Lecture Last class we saw that volcanic activity is encountered at DIVERGENT and CONVERGENT PLATE BOUNDARIES. We saw that DIVERGENT plate boundaries and their corresponding volcanoes are particularly important along the mid-ocean RIDGES. Furthermore, CONVERGENT PLATE BOUNDARIES can result in the sinking of one TECTONIC PLATE beneath another creating SUBDUCTION ZONES. 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). 2 REVIEW: Previous Lecture 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. Thus, STRATOVOLCANOES are volcanoes that are typically found along SUBDUCTION ZONES. Are all volcanoes cone-shaped STRATOVOLCANOES? Are all volcanoes found along PLATE BOUNDARIES? 3 REVIEW: Previous Lecture 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. Thus, STRATOVOLCANOES are volcanoes that are typically found along SUBDUCTION ZONES. Are all volcanoes cone-shaped STRATOVOLCANOES? Are all volcanoes found along PLATE BOUNDARIES? 4 Mantle Plumes: Volcanic Activity Far from Plate Boundaries Hawaii – tropical paradise. Hawaii consists of multiple VOLCANIC ISLANDS very far from any PLATE BOUNDARIES. These islands sit in the middle of the TECTONIC PLATE known as the HAWAIIAN ISLANDS PACIFIC PLATE. Why then are we encountering volcanic activity here? Did you know there will one day be another Hawaiian island? 5 Mantle Plumes: Volcanic Activity Far from Plate Boundaries PLUME (definition): Spreading out in the shape of a feather. MANTLE PLUMES consist of extremely hot MAGMA originating at the CORE-MANTLE boundary. The CORE heats the MAGMA that slowly gets pumped into the MANTLE (see figure A below), rising it up towards the LITHOSPHERE. 6 Mantle Plumes: Volcanic Activity Far from Plate Boundaries Given its extremely high temperature, it can melt its way through the MANTLE and towards the LITHOSPHERE. The head of the MANTLE PLUME spreads out (like a mushroom) just below the LITHOSPHERE, melting surrounding UPPER MANTLE rock (see figure B below). At this point, there are two possibilities. 7 Mantle Plumes: Volcanic Activity Far from Plate Boundaries Possibility 1: MAGMA can gradually cool beneath the surface, creating lots of volcanic rock (known as IGNEOUS ROCK). Possibility 2: The HOT SPOT (i.e., MAGMA beneath the surface) causes a volcanic eruption. Such volcanoes are known as HOT SPOT VOLCANOES as they are fed by the pool of HOT MAGMA just below the surface. Possibility 2 is what we are observing in the Hawaiian Islands (see figure C below). 8 Mantle Plumes: Volcanic Activity Far from Plate Boundaries The Hawaiian Islands are a trail of HOT SPOT VOLCANOES. THINKING QUESTION: But why do we observe this trail of islands and not just one huge volcanic island? FUTURE ISLAND OLDEST ISLAND YOUNGEST ISLAND TRAIL OF HAWAIIAN ISLANDS 9 Mantle Plumes: Volcanic Activity Far from Plate Boundaries THINKING QUESTION: But why do we observe this trail of islands and not just one huge volcanic island? Given that MANTLE PLUME originates below the LITHOSPHERE, its position remains fixed and is NOT affected by the moving TECTONIC PLATE above it. As LITHOSPHERE (i.e., TECTONIC PLATE) moves, MAGMA escapes onto the surface at different sites, creating multiple islands! A future Hawaiian island is already on the way beneath the ocean! FUTURE ISLAND!!! OLDEST ISLAND YOUNGEST ISLAND Loihi, now referred to as Kama’ehuakanaloa DIRECTION OF PLATE MOVEMENT TRAIL OF HAWAIIAN ISLANDS 10 Mantle Plumes: Volcanic Activity Far from Plate Boundaries What do the volcanoes above HOT SPOTS, as we encounter in Hawaii look like? Kilauea is a volcano on the Hawaiian Island known as Hawaii (the youngest island in the chain). It has been erupting for approximately 30 years now…. Recent eruption in September 2023!!! Yet people travel to Hawaii. Shouldn’t they be worried? Kilauea erupting. Notice long rivers of MAGMA. The composition of the MAGMA here means there is far less risk. Eruptions less violent. 11 Mantle Plumes: Volcanic Activity Far from Plate Boundaries The composition of the MAGMA a Kilauea means there is far less risk. Remember the gummy magma and the gases associated with STRATOVOLCANO eruptions along SUBDUCTION ZONES? This was largely due to all the silica in the MAGMA resulting from the sinking of one TECTONIC PLATE beneath another. There is no such thing at Kilauea as it is far from any PLATE BOUNDARIES. Thus, its MAGMA has far less silica and is therefore less sticky. Less silica also means less gases! Volcanoes like Kilauea erupt less violently and release a very fluid MAGMA that can flow much more easily away from the eruption site. This means less danger! Such volcanoes, whose MAGMA (and therefore LAVA) are more fluid, have a different shape. They are known as SHIELD VOLCANOES (see examples on next page). 12  Stratovolcanoes vs. Shield Volcanoes Let’s compare our STRATOVOLCANOES to SHIELD VOLCANOES: STRATOVOLCANO STRATOVOLCANO STRATOVOLCANO MOUNT SAINT HELENS (USA) MOUNT VESUVIUS (ITALY) MAYON (THE PHILIPPINES) SHIELD VOLCANO SHIELD VOLCANO MOUNT KARTHALA PITON DE LA FOURNAISE MOUNT TERROR (COMOROS) (French but near Madagascar) (ANTARCTICA) 13 Shield Volcano Magma: From far below To further explain the MAGMA coming from SHIELD VOLCANOES, let us consider Earth’s main chemical composition at different depths. MANTLE PLUMES originate at the CORE- MANTLE boundary. CORE- MANTLE These MANTLE PLUMES feed hot MAGMA to BOUNDARY SHIELD VOLCANOES above HOT SPOTS. While the MAGMA may contain some silica and aluminum from melted MANTLE ROCK, there will be far less than is encountered at SUBDUCTION ZONES. At SUBDUCTION ZONES, huge amounts of Silica (SiO2) consists of SILICON and OXYGEN. The silica and aluminum enter MAGMA as one deeper you go, the less abundant these (and aluminum) TECTONIC PLATE sinks beneath another. become. 14 Shield Volcano Magma: From far below MAGMA coming from SHIELD VOLCANOES is less VISCOUS than MAGMA coming from STRATOVOLCANOES. VISCOSITY: Resistance of a fluid (i.e., a liquid or gas) to a change in shape or movement of neighboring portions relative to one another. VISCOSITY (in everyday terms): how gummy, thick or sticky a fluid is; how much a fluid resists or opposes flow. Honey, maple syrup, corn syrup, motor oil are all MORE VISCOUS (i.e., have a greater VISCOSITY) than water. Again, MAGMA from SHIELD VOLCANOES is LESS VISCOUS than MAGMA from STRATOVOLCANOES. This has a huge impact on the shape of both these volcanoes. 15 Shield Volcano Magma: From far below MAGMA coming from SHIELD VOLCANOES is less VISCOUS than MAGMA coming from STRATOVOLCANOES. MAGMA from SHIELD VOLCANOES can travel GREATER distances, spread out in thin layers, slope gradually. It does not get stuck or resist flow like VISCOUS magma from STRATOVOLCANOES. BASALT MAGMA (and therefore LAVA) from SHIELD VOLCANOES is: rich in IRON and MAGNESIUM does not contain much silica This LAVA solidifies to form DENSE (high density or mass ÷ volume) BASALTIC ROCK (i.e., BASALT). BASALTIC ROCK makes up majority of ocean floor (due to all the volcanic activity in oceans). Lava solidifying to form BASALT 16 Anatomy of a Shield Volcano MAGMA coming from SHIELD VOLCANOES is less VISCOUS than MAGMA coming from STRATOVOLCANOES. How do SHIELD VOLCANOES look? From above, like an Ancient Greek shield. That’s where that name comes from! ANCIENT GREEK SHIELD SHIELD VOLCANOES have: wide DOME (the circular mound that sticks out of the ground) with a gradual slope (not steep like STRATOVOLCANOES). wide dome consists of MANY LAVA layers. NOTE: a CALDERA (see picture) may form (not always) when surrounding stone collapses into hole/space that once contained SHIELD VOLCANO ON molten stone (MAGMA) released as LAVA during an eruption. MARS!!! 17 Anatomy of a Shield Volcano MAGMA coming from SHIELD VOLCANOES is less VISCOUS than MAGMA coming from STRATOVOLCANOES. SHIELD VOLCANO How do SHIELD VOLCANOES look? From above, like an Ancient Greek shield. That’s where that WIDE DOME, name comes from! NOT STEEP SHIELD VOLCANOES have: wide DOME (the circular mound that sticks out of the ground) with a gradual slope (not steep like STRATOVOLCANOES). wide dome consists of MANY LAVA layers. NOTE: a CALDERA (see picture) may form (not always) when surrounding stone collapses into hole/space that once contained molten stone (MAGMA) released as LAVA during an eruption. 18 Stratovolcano Magma: Lower Density, Higher Viscosity MAGMA coming from STRATOVOLCANOES is more VISCOUS than MAGMA coming from SHIELD VOLCANOES. Due to materials carried into MAGMA by plate SUBDUCTION, STRATOVOLCANO MAGMA (and LAVA) contains far more SILICA and ALUMINUM than MAGMA from SHIELD VOLCANOES. ANDESITE This makes it LESS DENSE (i.e., lower density). SILICA also makes this MAGMA (and LAVA) thicker, stickier and more resistant to flow. This LAVA solidifies to form a variety of rocks, with most common being ANDESITE. ANDESITE is named after ANDES mountains and is 52 – 63% by weight SILICA! Lava solidifying to form ANDESITE 19 Anatomy of a Stratovolcano MAGMA coming from STRATOVOLCANOES is more STRATOVOLCANO VISCOUS than MAGMA coming from SHIELD VOLCANOES. How do STRATOVOLCANOES look? NARROW DOME, STRATOVOLCANOES have: STEEPER narrower DOME (the circular mound that sticks out of the ground) with a steeper slope. they are what most of us picture when we imagine a volcano! NOTE: a CALDERA (see picture) may form (not always) when surrounding stone collapses into hole/space that once contained molten stone (MAGMA) released as LAVA during an eruption. 20  Stratovolcanoes vs. Shield Volcanoes: REVISITED Let’s compare our STRATOVOLCANOES to SHIELD VOLCANOES: STRATOVOLCANO STRATOVOLCANO STRATOVOLCANO MOUNT SAINT HELENS (USA) MOUNT VESUVIUS (ITALY) MAYON (THE PHILIPPINES) SHIELD VOLCANO SHIELD VOLCANO MOUNT KARTHALA PITON DE LA FOURNAISE MOUNT TERROR (COMOROS) (French but near Madagascar) (ANTARCTICA) 21 CINDER CONES – The Baby of the Family CINDER CONES are tiny (generally less than 400 m tall), steep volcanoes made up of PYROCLASTIC ROCKS such as SCORIA. CINDER CONE CINDER CONES are often referred to as SCORIA CONES. What on Earth is a PYROCLASTIC ROCK? The answer is in the name! PYRO = Greek for FIRE CLASTIC = broken. PYROCLASTIC ROCKS (like SCORIA) are rocks generated by volcanic activity and that consist of fragments of other rocks and minerals! Very small PYROCLASTIC MATERIALS (i.e., fragments less than 2 mm in size) are what we refer to as ASH. 22 CINDER CONES – The Baby of the Family As for SCORIA, they are bits of LAVA that harden in midair after being ejected by a volcano’s gases. CINDER CONE eruptions are violent, ejecting molten PYROCLASTIC materials (such as SCORIA) into the air. SCORIA does not fly far from the volcano’s vent (hole), making CINDER CONES steep in shape. SCORIA A CINDER CONE in California, USA A CINDER CONE in B.C., Canada 23 LAVA DOMES – aka VOLCANIC DOMES LAVA DOMES (i.e., VOLCANIC DOMES) are very small volcanoes that possess extremely viscous (extremely thick) MAGMA and LAVA. The LAVA does not move far at all and continues to pile up just outside the volcano’s vent (i.e., hole). LAVE DOMES are often found next to larger STRATOVOLCANOES. A LAVA DOME associated with the far larger A LAVA DOME associated with the Santa Maria STRATOVOLCANO, Mount Saint Helens volcano in Guatemala. (Washington State, USA) 24 Take a Bow – the 4 Volcano Types A nice image comparing the 4 types of volcanoes we have examined! 25 Thank you for listening! 26  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