Tectonics PDF

Topic 1 Plate Tectonics 1.1 Plate Tectonic Theory Definitions: Lithosphere The crust and uppermost solid part of the mantle. Tectonic plates Pieces of rock that make up the lithosphere. They can contain continental and/or oceanic crust. Plate movement...

Topic 1 Plate Tectonics 1.1 Plate Tectonic Theory Definitions: Lithosphere The crust and uppermost solid part of the mantle. Tectonic plates Pieces of rock that make up the lithosphere. They can contain continental and/or oceanic crust. Plate movement The movement of tectonic plates relative to each other. This results in the formation of landforms and tectonic phenomena. Internal structure of the Earth The Earth has a layered structure consisting of the core, mantle, and crust. Asthenosphere The semi-solid upper mantle that lies below the lithosphere. Plate boundaries Where plates may move away from each other, move towards each other, or slide past each other. Convection currents Currents of heat within the hot softened mantle below the crust, generated by the heat from the Earth's core, which drive tectonic plate movements. Slab-pull force Gravitational force that causes a denser oceanic plate to sink further into the mantle under its own weight. Divergent plate boundaries Where plates move away from each other. Convergent plate boundaries Where plates move towards each other. Transform plate boundaries Where plates slide past each other. Subduction The process of an oceanic plate colliding and descending beneath another less dense tectonic plate. The plate tectonic theory explains that: Earth has a three- Layers, Position, Temperature and Thickness of the Earth’s structure layered structure Layers Position Temperature Thickness Core innermost Highest, 4400 – 6000 °C Thickest, 3300 km Mantle In between 1000 – 3700 °C 2900 km Crust outermost Lowest Thinnest, 6 – 70 km The Earth's The uppermost part of the mantle and the crust are the solid parts of the Earth. lithosphere is broken Together, they are known as the lithosphere. up into huge pieces The lithosphere is divided into huge pieces called tectonic plates. There are two types of crusts that make up tectonic plates: called tectonic 1. Continental (make up the land masses) plates. 2. Oceanic (make up the seafloor; denser than continental plate) The semi-solid asthenosphere lies below the lithosphere. Heat from the core causes the rocks in the asthenosphere to melt. Plate movements give rise to three types of plate boundaries: 1. Divergent plate boundaries (plates are moving away from each other). 2. Convergent plate boundaries (plates are moving towards each other). 3. Transform plate boundaries (plates are sliding past each other). Tectonic plates are There are two forces that are responsible for plate movements: constantly moving. 1. Convection currents. Process: - Heat from the earth's core causes the mantle material to become less dense. - Mantle material rises towards the surface. - The rising convection currents then spread beneath the plates and drag them apart, causing divergent plate movement. - The mantle material then loses heat and sinks towards the core. - Convergent plate movement occurs where the convection currents collide. - The materials then get heated up again, and the process repeats. This rising and sinking of the mantle material forms convection currents. 2. Slab-pull force. Process: - When two plates converge, the denser oceanic crust is pulled down by gravity as it subducts beneath the less dense crust. - The denser oceanic crust sinks deeper into the mantle under its own weight. pulling the rest of the plate with it, contributing to further convergence. Plate movements result in formation of landforms (e.g. mountain ranges, oceanic trenches) and phenomena (e.g. earthquakes, tsunamis) 1.1 Checkpoint Compare the layers’ position, Layers, Position, Temperature and Thickness of the Earth’s structure temperature and thickness Layers Position Temperature Thickness Core innermost Highest, 4400 – 6000 °C Thickest, 3300 km Mantle In between 1000 – 3700 °C 2900 km Crust outermost Lowest Thinnest, 6 – 70 km How do convection currents cause Convection currents. tectonic plates to move?  Process: - Heat from the earth's core causes the mantle material to become less dense. - Mantle material rises towards the surface. - The rising convection currents then spread beneath the plates and drag them apart, causing divergent plate movement. - The mantle material then loses heat and sinks towards the core. - Convergent plate movement occurs where the convection currents collide. - The materials then get heated up again, and the process repeats. This rising and sinking of the mantle material forms convection currents. How does slab-pull force cause Slab-pull force. tectonic plates to move? Process: - When two plates converge, the denser oceanic crust is pulled down by gravity as it subducts beneath the less dense crust. - The denser oceanic crust sinks deeper into the mantle under its own weight. pulling the rest of the plate with it, contributing to further convergence. What is the difference between Landforms (e.g. mountain ranges, oceanic trenches) and phenomena (e.g. earthquakes, tsunamis) landforms and phenomena? 1.2 Seafloor spreading Definitions: Seafloor spreading A process where magma from deep within the Earth rises through mid-ocean ridges to create new oceanic crust. Mid-ocean ridge A submarine mountain chain linearly located on the ocean floor at divergent plate boundaries. Oceanic trench Deep depression found in the ocean floor where one oceanic plate is subducting beneath another plate. Seafloor spreading and how it supports plate tectonic theory: What is seafloor spreading? Why does the evidence of seafloor spreading support the plate tectonic theory?  The age of rocks at the seabed shows a pattern: - Rocks nearer to the crest (centre) of the mid-ocean ridge are the youngest. - Rocks further away from the ridge are progressively older.  Shows how new oceanic crust is created at divergent boundaries and then moves laterally on both sides of the mid-ocean ridge as seafloor spreading continues.  Little sediment accumulation is found at oceanic trenches, as older oceanic crust is being destroyed at oceanic trenches.  As a result, oceanic crusts are usually younger than continental crusts.  Proves that new crust is continually formed at divergent boundaries at the mid-ocean ridges, and as plates move, older crust is destroyed further away at oceanic trenches. Process: - Where two plates move away from each other at divergent plate boundaries, seafloor spreading occurs. - Magma from deep within the earth rises through the mid-ocean ridge. - New oceanic crust is formed. 1.2 Checkpoint Question Answer What is seafloor spreading? Process: - Where two plates move away from each other at divergent plate boundaries, seafloor spreading occurs. - Magma from deep within the earth rises through the mid-ocean ridge. - New oceanic crust is formed.  How does the evidence of  The age of rocks at the seabed shows a pattern: seafloor spreading support - Rocks nearer to the crest (centre) of the mid-ocean ridge are the youngest. the plate tectonic theory? - Rocks further away from the ridge are progressively older.  Shows how new oceanic crust is created at divergent boundaries and then moves laterally on both sides of the mid-ocean ridge as seafloor spreading continues.  Little sediment accumulation is found at oceanic trenches, as older oceanic crust is being destroyed at oceanic trenches.  As a result, oceanic crusts are usually younger than continental crusts.  Proves that new crust is continually formed at divergent boundaries at the mid-ocean ridges, and as plates move, older crust is destroyed further away at oceanic trenches. 1.3 Magnetic striping Definitions: Geographic North The direction towards the fixed point on Earth called the North Pole. Geographic South The direction towards the fixed point on Earth called the South Pole. Magnetic North Direction that a compass needle points to. This is the direction of the Earth's magnetic North pole, where the Earth acts as a magnet itself. Magnetic South The South direction that a compass needle points to. This is the direction of the Earth's magnetic South pole. Normal polarity When the Earth's magnetic North points towards geographic North and magnetic South points towards geographic South. Reverse polarity When the Earth's magnetic North points towards geographic South and magnetic South points towards geographic North. Magnetic striping and how the evidence of magnetic striping supports the plate tectonic theory What is magnetic striping? Occurs as: Why does evidence of magnetic striping support the plate tectonic theory?  Earth has a geographic North and a geographic South as well as a - Basaltic rocks from the oceanic crust are volcanic rocks formed  This zebra-like pattern is symmetrical on either side of mid-ocean magnetic North and magnetic South. from iron-rich lava ridges, showing that this is not a random or isolated occurrence.  The geographic North and geographic South do not change. - They contain magnetic materials When the iron-rich lava erupts, it  Provides evidence that plates move, supporting the plate  However, the magnetic North and magnetic South can shift, and cools and solidifies tectonics theory as: they have reversed multiple times over geological time. - Its magnetic materials points towards Earth's magnetic North, - Oceanic plates move away from each other.  Currently, the magnetic North points roughly towards the recording evidence of Earth's polarity at that time - Iron-rich lava erupts from the centre of the ridge. geographic North, and the magnetic South points roughly towards - Lava cools, solidifies, and forms new oceanic crust. the geographic South- this is known as normal polarity. - The crust is then pushed in both directions away from the ridge  Reverse polarity happens when the magnetic North points roughly when new lava erupts and solidifies as plates move apart. towards the geographic South, and the magnetic South points - When Earth's polarity reverses, the rocks record the reversals. roughly towards the geographic North. - Over time, as more lava moves away from the ridge due to plate  Over geological time, the Earth's polarity has flipped multiple divergence, a symmetrical zebra-like pattern forms. times, alternating between normal and reverse polarity  Magnetic striping is the zebra-like pattern where there are strips of normal polarity rocks alternating alongside strips of reversed polarity rocks on the seafloor It is symmetrical on both sides of the mid-ocean ridge  1.3 Checkpoint Questions Answer Why does magnetic striping occur? - Basaltic rocks from the oceanic crust are volcanic rocks formed from iron-rich lava - They contain magnetic materials When the iron-rich lava erupts, it cools and solidifies - Its magnetic materials points towards Earth's magnetic North, recording evidence of Earth's polarity at that time How does magnetic striping support plate tectonic theory?  This zebra-like pattern is symmetrical on either side of mid-ocean ridges, showing that this is not a random or isolated occurrence.  Provides evidence that plates move, supporting the plate tectonics theory as: - Oceanic plates move away from each other. - Iron-rich lava erupts from the centre of the ridge. - Lava cools, solidifies, and forms new oceanic crust. - The crust is then pushed in both directions away from the ridge when new lava erupts and solidifies as plates move apart. - When Earth's polarity reverses, the rocks record the reversals. - Over time, as more lava moves away from the ridge due to plate divergence, a symmetrical zebra-like pattern forms. 1.4 Tectonic processes at different plate boundaries Definitions: Volcano Landform created when lava erupts onto the Earth's surface. Rift valley Linear lowland region with steep sides. Earthquake Shaking of the ground due to the sudden release of energy when two plates suddenly slip past each other. Fold mountain Mountains that are formed due to two converging plates that cause the Earth's layers to fold. Fault A fracture along which the blocks of crust on either side have moved relative to one another. Tectonic plate boundaries Divergent plate boundary is where two tectonic plates move apart Convergent is where two tectonic plates move towards each other. Transform is where two tectonic plates slide past each other. Oceanic-oceanic divergent plate boundary between the North American Oceanic-oceanic convergent plate boundary between the Philippine San Andreas Fault where the Pacific Plate slides past the North Plate and the Eurasian Plate Plate and the Pacific Plate. American Plate. Continental-continental divergent plate boundary between the Nubian Continental-continental convergent plate boundary between the Plate and Somalian Plate. Eurasian Plate and the Indo-Australian Plate Oceanic-continental convergent plate boundary between the Nazca Plate and the South American Plate. Landforms and Phenomenas created in plate boundaries Divergent plate boundary is where two tectonic plates move apart Convergent is where two tectonic plates move towards each other. Transform is where two tectonic plates slide past each other. Tectonic plates are moving apart from each other, resulting in mid-ocean Tectonic plates are moving towards each other, resulting in fold Tectonic plates slide past each other. No crust is created or destroyed ridges, volcanoes including submarine volcanoes and volcanic islands, riff mountains, volcanoes including submarine volcanoes and volcanic systems, and earthquakes. islands, oceanic trenches, and earthquakes. Oceanic-oceanic divergent plate boundary between the North American Oceanic-oceanic convergent plate boundary between the Philippine San Andreas Fault where the Pacific Plate slides past the North Plate and the Eurasian Plate Plate and the Pacific Plate. American Plate. Process: Process: Process: - Stress caused by the plate movement produces a fault, which is a - Two oceanic plates move apart. - Two oceanic plates collide. zone of fractures. - The denser plate subducts beneath the other plate. - Earthquakes occur here as one plate suddenly slips past another.  - The decrease in overlying pressure causes parts of the underlying - This forms a deep depression known as an oceanic trench - Magma does not rise to Earth's surface, hence there are no mantle to melt, forming magma. - As the subducting plate sinks into the mantle, the high pressure volcanoes. - Magma rises through weak areas in the crust to the Earth's surface, forces water out of its oceanic crust. Water lowers the melting and fills gaps caused by the Uspreading plates. point of the overlying mantle, causing it to melt, forming Example: magma. Pacific Plate sliding past the North American plate. This forms the San  Lava cools and solidifies to form basaltic rocks. The rocks make up - Magma rises through weak areas in the crust to the Earth's Andreas Fault in California, USA. Earthquakes are common here. Such a new oceanic crust. surface as the 1989 Loma Prieta earthquake in California.  An extensive underwater mountain chain - the mid-ocean ridge - - This forms a chain of volçanoes, known as a volcanic island. forms. Example: The oceanic North American Plate and oceanic Eurasian Plate  Friction along the subducting oceanic plate also causes move apart. This forms the Mid-Atlantic Ridge. earthquakes to occur. Example:  At the centre of the ridge is a deep rift valley with steep sides. The oceanic Pacific Plate subducts beneath the oceanic Philippine  Magma rises through weak areas in the crust to the Earth's surface, Plate. This forms the Mariana Trench, as well as volcanic islands forming submarine volcanoes. known as the Mariana Islands. Guam, an island near the Mariana  After many eruptions, the volcanoes may break the surface of the Trench, commonly experiences earthquakes. ocean to form volcanic islands, such as in Surtsey, Iceland.  Earthquakes also occur here due to the stress and tension released when plates move. [O-O Divergent: Mid-atlantic Ridge, deep rift valley, volcanoes, earthquakes] Continental-continental divergent plate boundary between the Nubian Continental-continental convergent plate boundary between the Plate and Somalian Plate. Eurasian Plate and the Indo-Australian Plate Process: - Two continental plates move apart. Process: - Rocks eventually fracture to form parallel faults. - Two continental plates collide - The rock between these faults collapses to form a deep rift valley - Subduction does not take place because continental plates are with steep sides. too buoyant to subduct - As the plates move apart, the decrease in overlying pressure - Enormous pressure causes the rocks to be uplifted and buckled causes parts of the underlying mantle to melt, forming magma. to form fold mountains. Magma rises through weak areas in the crust to the Earth's surface, forming volcanoes.  Friction along the convergent plate boundary also causes earthquakes to occur.  Earthquakes occurs as stress and tension are released when plates  Magma does not rise to the surface, hence no volcanoes are move. formed Example: Example: Continental Indo-Australian Plate converges with the continental Eurasian Plate. This forms the Himalayan Mountain range. - The Nubian Plate pulls apart from the Somalian Plate. This area experiences many earthquakes, such as the devastating 2015 - This forms the Great Rift Valley. Nepal earthquake. - Examples of volcanoes formed: Mount Kenya, Mount Kilimanjaro. [C-C Divergent: Deep rift valley, volcanoes, earthquakes] Oceanic-continental convergent plate boundary between the Nazca Plate and the South American Plate. Process: - An oceanic plate collides with a continental plate. - The denser oceanic plate subducts beneath the continental plate. - This forms an oceanic trench in the subduction zone. - As the subducting plate sinks into the mantle, the high pressure forces water out of its oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma. - Magma rises through weak areas in the crust to the Earth's surface, forming volcanoes on the continental plate.  Friction along the subducting oceanic plate causes earthquakes to occur. - Enormous pressure at this plate boundary causes rocks on the continental plate to be uplifted and buckled, forming fold mountains. Example: Oceanic Nazca Plate converges with the continental South American Plate. Denser Nazca Plate subducts beneath the South American Plote forming: 1. The Peru-Chile trench. 2. The Andes fold mountain range. 3. The Nevado del Ruiz volcano. Earthquakes are also common here, such as the 2010 Chile earthquake.  1.4 Checkpoint Questions Answers What are the Divergent plate boundary is where two tectonic plates move apart landforms and/or Tectonic plates are moving apart from each other, resulting in mid-ocean ridges, volcanoes including submarine volcanoes and volcanic islands, riff systems, and earthquakes. phenomenas taking Oceanic-oceanic divergent plate boundary between the North American Plate and the Eurasian Plate place at divergent plate boundary? Process: - Two oceanic plates move apart. - The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma. - Magma rises through weak areas in the crust to the Earth's surface, and fills gaps caused by the spreading plates.  Lava cools and solidifies to form basaltic rocks. The rocks make up a new oceanic crust.  An extensive underwater mountain chain - the mid-ocean ridge - forms. Example: The oceanic North American Plate and oceanic Eurasian Plate move apart. This forms the Mid-Atlantic Ridge.  At the centre of the ridge is a deep rift valley with steep sides.  Magma rises through weak areas in the crust to the Earth's surface, forming submarine volcanoes.  After many eruptions, the volcanoes may break the surface of the ocean to form volcanic islands, such as in Surtsey, Iceland.  Earthquakes also occur here due to the stress and tension released when plates move. [O-O Divergent: Mid-atlantic Ridge, deep rift valley, volcanoes, earthquakes] Continental-continental divergent plate boundary between the Nubian Plate and Somalian Plate. Process: - Two continental plates move apart. - Rocks eventually fracture to form parallel faults. - The rock between these faults collapses to form a deep rift valley with steep sides. - As the plates move apart, the decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma. Magma rises through weak areas in the crust to the Earth's surface, forming volcanoes.  Earthquakes occurs as stress and tension are released when plates move. Example: - The Nubian Plate pulls apart from the Somalian Plate. - This forms the Great Rift Valley. - Examples of volcanoes formed: Mount Kenya, Mount Kilimanjaro. [C-C Divergent: Deep rift valley, volcanoes, earthquakes] What are the Convergent is where two tectonic plates move towards each other. landforms and/or Tectonic plates are moving towards each other, resulting in fold mountains, volcanoes including submarine volcanoes and volcanic islands, oceanic trenches, and earthquakes. phenomenas taking Oceanic-oceanic convergent plate boundary between the Philippine Plate and the Pacific Plate. place at convergent plate boundary? Process: - Two oceanic plates collide. - The denser plate subducts beneath the other plate. - This forms a deep depression known as an oceanic trench - As the subducting plate sinks into the mantle, the high pressure forces water out of its oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma. - Magma rises through weak areas in the crust to the Earth's surface - This forms a chain of volçanoes, known as a volcanic island.  Friction along the subducting oceanic plate also causes earthquakes to occur. Example: The oceanic Pacific Plate subducts beneath the oceanic Philippine Plate. This forms the Mariana Trench, as well as volcanic islands known as the Mariana Islands. Guam, an island near the Mariana Trench, commonly experiences earthquakes. Continental-continental convergent plate boundary between the Eurasian Plate and the Indo-Australian Plate  Process: - Two continental plates collide - Subduction does not take place because continental plates are too buoyant to subduct - Enormous pressure causes the rocks to be uplifted and buckled to form fold mountains.  Friction along the convergent plate boundary also causes earthquakes to occur.  Magma does not rise to the surface, hence no volcanoes are formed Example: Continental Indo-Australian Plate converges with the continental Eurasian Plate. This forms the Himalayan Mountain range. This area experiences many earthquakes, such as the devastating 2015 Nepal earthquake. Oceanic-continental convergent plate boundary between the Nazca Plate and the South American Plate. Process: - An oceanic plate collides with a continental plate. - The denser oceanic plate subducts beneath the continental plate. - This forms an oceanic trench in the subduction zone. - As the subducting plate sinks into the mantle, the high pressure forces water out of its oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma. - Magma rises through weak areas in the crust to the Earth's surface, forming volcanoes on the continental plate.  Friction along the subducting oceanic plate causes earthquakes to occur. - Enormous pressure at this plate boundary causes rocks on the continental plate to be uplifted and buckled, forming fold mountains. Example: Oceanic Nazca Plate converges with the continental South American Plate. Denser Nazca Plate subducts beneath the South American Plote forming: 4. The Peru-Chile trench. 5. The Andes fold mountain range. 6. The Nevado del Ruiz volcano. Earthquakes are also common here, such as the 2010 Chile earthquake. What are the Transform is where two tectonic plates slide past each other. landforms and/or Tectonic plates slide past each other. No crust is created or destroyed phenomenas taking San Andreas Fault where the Pacific Plate slides past the North American Plate. place at transform plate boundary? Process: - Stress caused by the plate movement produces a fault, which is a zone of fractures. - Earthquakes occur here as one plate suddenly slips past another. - Magma does not rise to Earth's surface, hence there are no volcanoes. Example: Pacific Plate sliding past the North American plate. This forms the San Andreas Fault in California, USA. Earthquakes are common here. Such as the 1989 Loma Prieta earthquake in California. 2. 1 Tectonics processes affecting the magnitude of earthquakes Definitions: Seismic waves Energy released during an earthquake. Focus The point in the Earth's crust where seismic waves are released. Epicentre The point on the Earth's surface directly above the focus. Seismometer Instrument used to determine the magnitude of earthquakes. Magnitude A measure of the amount of seismic energy. Tectonic processes result in earthquakes Earthquakes refer to the shaking of the Earth's ground due to the sudden release of energy in the Earth's lithosphere. Earthquakes generally occur along plate boundaries, which contain systems of deep fractures called faults. Earthquakes occur when: - Rock masses on either side of a fault are pushed by tectonic forces. - Friction causes them to get locked, and stress builds up. When the stress exceeds the strength of the fault (or rock), the rocks snap or suddenly move to a new position. - This sudden movement causes seismic waves to be released, resulting in ground shaking. The point in the earth's crust where seismic waves are released is known as focus. - The focus is the origin of the earthquake. The point on the Earth's surface directly above the focus is called the epicentre. - Shaking is generally felt most strongly near the epicentre. Earthquake measurement Earthquakes are measured using seismometers. These are sensitive instruments that detect ground vibrations and determine the magnitude of an earthquake. The greater the seismic energy released during an earthquake, the greater the magnitude. Richter Scale (ML). Moment Magnitude Scale (Mw).  The Richter Scale calculates earthquake magnitude using the height of the largest wave recorded on  The Mw scale rates earthquake magnitude based on the total energy released during the earthquake. seismometers.  It estimates the total energy released during an earthquake instead of just the largest wave like the  Thus, earthquake magnitude is measured based on the maximum seismic intensity reached, rather Richter Scale. than the total seismic energy released throughout the earthquake.  Hence, it is generally more accurate, especially in measuring earthquakes of magnitude 8 and above.  The scale is numbered from 1 to 10, with 10 being the greatest magnitude. Scientists have adjusted the magnitudes of past earthquakes which were initially measured using the Richter Scale.   Scale is logarithmic - an earthquake of magnitude 6 releases about 32 fimes more energy than a magnitude 5 earthquake. Example: Prince William Sound Earthquake in Alaska. USA, in 1964 was initially rated 8.6 on the Richter Scale,  However, the Richter Scale has a limitation: but was later adjusted to 9.2 based on the Mw scale. - The Richter scale would rate an earthquake with a single drastic spike in wave energy as having a higher  Like the Richter Scale, the Mw scale is also logarithmic - an earthquake of magnitude 6 releases about magnitude than a long earthquake with many large, intense waves. 32 times more energy than a magnitude 5 earthquake. - This underestimates longer earthquakes which release more overall energy by rating them as having lower magnitudes even though they are likely to do more damage. - Hence, the Richter Scale is no longer commonly used, except small, local earthquakes. 2.1 Checkpoint What is an earthquake? Earthquakes refer to the shaking of the Earth's ground due to the sudden release of energy in the Earth's lithosphere. What is the richter scale and its  The Richter Scale calculates earthquake magnitude using the height of the largest wave recorded on seismometers. disadvantage?  Thus, earthquake magnitude is measured based on the maximum seismic intensity reached, rather than the total seismic energy released throughout the earthquake.  The scale is numbered from 1 to 10, with 10 being the greatest magnitude.  Scale is logarithmic - an earthquake of magnitude 6 releases about 32 fimes more energy than a magnitude 5 earthquake.  However, the Richter Scale has a limitation: - The Richter scale would rate an earthquake with a single drastic spike in wave energy as having a higher magnitude than a long earthquake with many large, intense waves. - This underestimates longer earthquakes which release more overall energy by rating them as having lower magnitudes even though they are likely to do more damage. - Hence, the Richter Scale is no longer commonly used, except small, local earthquakes. What is the Moment Magnitude  The Mw scale rates earthquake magnitude based on the total energy released during the earthquake. Scale (Mw)?  It estimates the total energy released during an earthquake instead of just the largest wave like the Richter Scale.  Hence, it is generally more accurate, especially in measuring earthquakes of magnitude 8 and above. Scientists have adjusted the magnitudes of past earthquakes which were initially measured using the Richter Scale. Example: Prince William Sound Earthquake in Alaska. USA, in 1964 was initially rated 8.6 on the Richter Scale, but was later adjusted to 9.2 based on the Mw scale.  Like the Richter Scale, the Mw scale is also logarithmic - an earthquake of magnitude 6 releases about 32 times more energy than a magnitude 5 earthquake. 2.2 Tectonic processes affecting the magnitude of volcanic eruptions Definitions: Lava Molten rocks that have erupted onto Earth's surface: it is called magma when found below the Earth's surface. Crater Bowl-shaped depression at the top of the volcano. Active vent An opening on the Earth's surface through which lava erupts. It is situated at the bottom of the crater. Conduit A central passageway in the volcano through which magma travels. It connects the magma chamber to the vent. Volcanic cone The triangle-shaped hill or mountain formed as lava accumulates around the vent. Magma chamber Location in the Earth's crust where magma is located. Viscous Thick, sticky consistency. Effusive A relatively gentle eruption that is mainly dominated by the outpouring of Iava onto the ground (as opposed to explosive eruptions which involve the violent ejection of tephra). Tephra Any type and size of rock fragment that is forcibly ejected from the volcano and travels an airborne path during an eruption (including ash and volcanic bombs). Tectonic processes result in volcanic eruptions  A volcano is a landform created when lava erupts onto the Earth's surface, and it may form a cone-shaped mountain as more lava erupts a accumulates over time.  Volcanic eruptions occur at: divergent plate boundaries convergent plate boundaries Divergent plate boundaries Convergent plate boundaries Process: Process: - Plates move apart, the crust stretches and fractures develop. - Plates move towards each other and the denser plate subducts under the other. - The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma. - As the subducting plate sinks into the mantle, the high pressure forces water out its oceanic crust. - Magma contains dissolved gases and is less dense than the surrounding materials. - Water lowers the melting point of the overlying mantle, causing it to melt, forming magma. - Therefore, magma rises through weak areas in the crust to the Earth's surface to erupt as lava, causing - Magma contains dissolved gases and is less dense than the surrounding materials. a volcanic eruption. - Therefore, magma rises through weak areas in the crust to the Earth's surface to erupt as lava, causing - The lava cools, solidifies and accumulates over time, forming a volcano. a volcanic eruption. - The lava cools, solidifies and accumulates over time, forming a volcano. Volcanic eruptions are more explosive than others:  The explosivity of volcanic eruptions depends on how easily dissolved has can escape from magma High silica magma Low silica magma - More viscous magma. - Less viscous magma. - As magma rises towards the Earth's surface, the dissolved gases in the magma cannot escape easily. - As magma rises towards the Earth's surface, the dissolved gases in the magma can escape easily. - More pressure builds up until gases escape explosively. - Less pressure builds up. - Resulting in violent, explosive eruptions. - Resulting in gentle, effusive eruptions. - Generally associated with stratovolcanoes. - Generally associated with shield volcanoes. - However there are volcanoes with viscous magma that do not result in explosive eruption as the magma rises in a way that allows gases to escape. - While Mount Merapi is a stratovolcano, its eruption in 2006 was not explosive as the viscous magma rose in a way that allowed dissolved gases to escape easily Stratovolcanoes Shield volcanoes Stratovolcanoes form when: Shield volcanoes form when: - High viscosity magma rises through weak areas in the crust to the earth's surface and erupts - Low viscosity magma rises through weak areas in the crust to the Earth's surface and erupts effusively. explosively as lava, ash and rocks. - Over successive eruptions, a volcano consisting of layers of lava develops. - The ash and rocks settle on the sides of the volcano, and are later covered by the lava. - As the less viscous lava travels a longer distance before cooling and solidifying, the volcano has gently - Over successive eruptions, a tall volcano consisting of alternating layers of ash and lava develops. sloping sides with a broad summit. - As the highly viscous lava travels a shorter distance before cooling and solidifying, the volcano has steep sides and a narrow summit. Example: Kilauea in Hawaii, USA. Example: Mount Mayon in the Philippines. Volcanic eruption measurement  The Volcanic Explosivity Index (VEl) measures the magnitude of different volcanic eruptions based on explosivity using the following criteria: - Volume of ejected material. The greater the volume of ejected material, the higher the VEI. - Height of the eruption cloud. The greater the height of the eruption cloud, the higher the VEI. - Duration of the eruption. The longer the eruption, the higher the VEI. Measured on a scale of 0 to 8.   Effusive eruptions are generally given a value of 0 or 1, as they are non-explosive with less than 0.0001 km of material ejected. Example: The ongoing effusive eruption of Kilauea, Hawai, which is non-explosive.  A value of 8 represents a mega-colossal explosive eruption that can eject more than 1,000km of tephra, with an eruption cloud column height of over 25km. Example: Toba Volcano in Northern Sumatra, Indonesia, 74,000 years ago. The volcano erupted approximately 2,800km of material, which covered india and parts of Southeast Asia in over 15 cm of ash.  VEl Scale is logarithmic - an increase of 1 on the VEl scale indicates an eruption 10 times more powerful than the number before it. 2.2 Checkpoint How do volcanic eruptions occur at divergent and convergent plate boundaries? Divergent plate boundaries Convergent plate boundaries Process: Process: - Plates move apart, the crust stretches and fractures - Plates move towards each other and the denser plate develop. subducts under the other. - The decrease in overlying pressure causes parts of the - As the subducting plate sinks into the mantle, the high underlying mantle to melt, forming magma. pressure forces water out its oceanic crust. - Magma contains dissolved gases and is less dense than the - Water lowers the melting point of the overlying mantle, surrounding materials. causing it to melt, forming magma. - Therefore, magma rises through weak areas in the crust to - Magma contains dissolved gases and is less dense than the the Earth's surface to erupt as lava, causing a volcanic surrounding materials. eruption. - Therefore, magma rises through weak areas in the crust to - The lava cools, solidifies and accumulates over time, the Earth's surface to erupt as lava, causing a volcanic forming a volcano. eruption. - The lava cools, solidifies and accumulates over time, forming a volcano. Why are volcanoes more explosive than others?  The explosivity of volcanic eruptions depends on how easily dissolved has can escape from magma High silica magma Low silica magma - More viscous magma. - Less viscous magma. - As magma rises towards the Earth's surface, the dissolved - As magma rises towards the Earth's surface, the dissolved gases in the magma cannot escape easily. gases in the magma can escape easily. - More pressure builds up until gases escape explosively. - Less pressure builds up. - Resulting in violent, explosive eruptions. - Resulting in gentle, effusive eruptions. - Generally associated with stratovolcanoes. - Generally associated with shield volcanoes. - However there are volcanoes with viscous magma that do not result in explosive eruption as the magma rises in a way that allows gases to escape. - While Mount Merapi is a stratovolcano, its eruption in 2006 was not explosive as the viscous magma rose in a way that allowed dissolved gases to escape easily Compare the characteristics of stratovolcanoes from shield volcanoes. Stratovolcanoes Shield volcanoes Stratovolcanoes form when: Shield volcanoes form when: - High viscosity magma rises through weak areas in the - Low viscosity magma rises through weak areas in the crust to the earth's surface and erupts explosively as lava, crust to the Earth's surface and erupts effusively. ash and rocks. - Over successive eruptions, a volcano consisting of layers - The ash and rocks settle on the sides of the volcano, and of lava develops. are later covered by the lava. - As the less viscous lava travels a longer distance before - Over successive eruptions, a tall volcano consisting of cooling and solidifying, the volcano has gently sloping alternating layers of ash and lava develops. sides with a broad summit. - As the highly viscous lava travels a shorter distance before cooling and solidifying, the volcano has steep sides and a Example: Kilauea in Hawaii, USA. narrow summit. Example: Mount Mayon in the Philippines. How are volcanic eruptions measured?  The Volcanic Explosivity Index (VEl) measures the magnitude of different volcanic eruptions based on explosivity using the following criteria: - Volume of ejected material. The greater the volume of ejected material, the higher the VEI. - Height of the eruption cloud. The greater the height of the eruption cloud, the higher the VEI. - Duration of the eruption. The longer the eruption, the higher the VEI. Measured on a scale of 0 to 8.  Effusive eruptions are generally given a value of 0 or 1, as they are non-explosive with less than 0.0001 km of material ejected. Example: The ongoing effusive eruption of Kilauea, Hawai, which is non-explosive.  A value of 8 represents a mega-colossal explosive eruption that can eject more than 1,000km of tephra, with an eruption cloud column height of over 25km. Example: Toba Volcano in Northern Sumatra, Indonesia, 74,000 years ago. The volcano erupted approximately 2,800km of material, which covered india and parts of Southeast Asia in over 15 cm of ash.  VEl Scale is logarithmic - an increase of 1 on the VEl scale indicates an eruption 10 times more powerful than the number before it. 2.3 Distributions of earthquakes, volcanoes and tectonic hazards Definitions: Distribution The way something is spread out or arranged over a geographic area. Pacific Ring of Fire A broad belt around the Pacific Ocean where most earthquakes and active volcanoes occur. Hot spot volcanoes Volcanoes that develop over extra hot regions in the mantle. These volcanoes may develop in locations away from plate boundaries. Soil liquefaction A phenomena whereby saturated, loose soil loses its soil structure and transforms into a thick fluid due to ground shaking. Pyroclastic flows Hot clouds of gas, ash, and rocks travelling down the slopes of a volcano. Lahars Mudflows comprising volcanic ash and water. Tsunami A series of ocean waves which can be caused by undersea earthquakes, volcanic eruptions and landslides. Distribution of Earthquakes and Volcanoes Distribution of Earthquakes Distribution of Volcanoes   Earthquakes occur along all types of plate boundaries.  Volcanoes are generally located near convergent and divergent plate boundaries.  The largest concentration of earthquakes is at the Pacific Ring of Fire.  At these plate boundaries, magma rises up to the surface, forming volcanoes.  At plate boundaries, plates are pushed by tectonic forces, stress builds up and energy is eventually  Belts of volcanoes may be observed along: released. - Convergent plate boundaries: A belt of volcanoes along subduction zones in the Pacific Ring of Fire. Examples: - Divergent plate boundaries: A belt of volcanoes along divergent plate boundaries between the North - Broad belt of earthquakes along convergent plate boundaries in the Pacific Ring of Fire. American and Eurasian plates. - Narrow belt of earthquakes along the divergent plate boundary at the Mid-Atlantic Ridge.  Unlike earthquakes, volcanoes are not found near: - Narrow belt of earthquakes along the transform plate boundary at the San Andreas Fault. - Transform plate boundaries. - Continental-continental convergent plate boundaries.  Earthquakes occur more commonly along convergent plate boundaries at subduction zones as more  At these boundaries, magma does not rise to the Earth's surface to form volcanoes. stress is bult up during subduction.  Hot spot volcanoes are exceptions that can be found away from plate boundaries.  Exception: Some earthquakes may occur away from plate boundaries such as within the Eurasian Example: The Piton de la Fournaise is a hot spot volcano located on the island of Réunion in the Indian Ocean, plate. away from plate boundaries.  The Pacific Ring of Fire is a broad belt around the Pacific Ocean where most earthquakes and active volcanoes occur.  Comprise all three types of plate boundaries. Examples: - Convergent: Pacific plate moving towards the Philippine plate. - Divergent: Pacific plate moving away from the Cocos plate. - Transform: Pacific plate sliding past the North American plate at the San Andreas Fault. Trend - Describe the general trend (pattern). Evidence - Use map evidence to support your answer e.g. names of tectonic plates and plate margins. You could also identify the Pacific Ring of Fire and the Mid-Atlantic Ridge. Anomalies - Identify any anomalies (examples that do not fit the general pattern). Trend - Describe the general trend (pattern). Evidence - Use map evidence to support your answer e.g. names of tectonic plates and plate margins. You could also identify the Pacific Ring of Fire and the Mid-Atlantic Ridge. Anomalies - Identify any anomalies (examples that do not fit the general pattern). Distribution of Tectonic Hazards Earthquake hazards Volcanic eruption hazards 1. Ground shaking 1. Tephra 2. Soil liquefaction 2. Volcanic gases 3. Landslides 3. Lava flows 4. Tsunamis 4. Pyroclastic flows 5. Lahars 6. Volcanic landslides  Earthquake hazards such as ground shaking, soil liquefaction and landslides are often  Similarly, volcanic hazards such as volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides are localised. often found around the volcanoes.  They are generally located within the same geographic region as the earthquake.  Since volcanoes are found along convergent and divergent plate boundaries, these hazards are also generally found  As earthquakes are found along plate boundaries, their hazards are also found near along these plate boundaries. plate boundaries.  However, not all tectonic hazards are localised. - Other hazards such as tsunamis and volcanic ash may spread beyond the geographic regions where earthquakes and volcanoes are located. - Tsunami waves and volcanic ash may travel thousands of kilometres from where they originated. - Tsunami waves can travel long distances without great loss of energy. Example: The 2004 Indian Ocean tsunami travelled almost 5000km to Africa with sufficient energy to cause deaths and destruction.  Ashfall can travel far from the geographic region where the volcanic eruption occurs. Example: During the eruption of Mount Pinatubo in 1991, ash spread across Southeast Asia. However, whether the dispersal of ash is localised or spreads far beyond the geographic region of the volcano is dependent on wind conditions as well as the volume of ash erupted and the height the ash is thrown into the atmosphere. 2.3 Checkpoint Question Answer Where are earthquakes distributed? Distribution of Earthquakes  Earthquakes occur along all types of plate boundaries.  The largest concentration of earthquakes is at the Pacific Ring of Fire.  At plate boundaries, plates are pushed by tectonic forces, stress builds up and energy is eventually released. Examples: - Broad belt of earthquakes along convergent plate boundaries in the Pacific Ring of Fire. - Narrow belt of earthquakes along the divergent plate boundary at the Mid-Atlantic Ridge. - Narrow belt of earthquakes along the transform plate boundary at the San Andreas Fault.  Earthquakes occur more commonly along convergent plate boundaries at subduction zones as more stress is bult up during subduction.  Exception: Some earthquakes may occur away from plate boundaries such as within the Eurasian plate.  The Pacific Ring of Fire is a broad belt around the Pacific Ocean where most earthquakes and active volcanoes occur.  Comprise all three types of plate boundaries. Examples: - Convergent: Pacific plate moving towards the Philippine plate. - Divergent: Pacific plate moving away from the Cocos plate. - Transform: Pacific plate sliding past the North American plate at the San Andreas Fault.  Where are volcanoes distributed? Distribution of Volcanoes  Volcanoes are generally located near convergent and divergent plate boundaries.  At these plate boundaries, magma rises up to the surface, forming volcanoes.  Belts of volcanoes may be observed along: - Convergent plate boundaries: A belt of volcanoes along subduction zones in the Pacific Ring of Fire. - Divergent plate boundaries: A belt of volcanoes along divergent plate boundaries between the North American and Eurasian plates.  Unlike earthquakes, volcanoes are not found near: - Transform plate boundaries. - Continental-continental convergent plate boundaries.  At these boundaries, magma does not rise to the Earth's surface to form volcanoes.  Hot spot volcanoes are exceptions that can be found away from plate boundaries. Example: The Piton de la Fournaise is a hot spot volcano located on the island of Réunion in the Indian Ocean, away from plate boundaries. Where are earthquake hazards distributed?  Earthquake hazards such as ground shaking, soil liquefaction and landslides are often localised.  They are generally located within the same geographic region as the earthquake.  As earthquakes are found along plate boundaries, their hazards are also found near plate boundaries. Where are volcanic eruption hazards distributed?  Similarly, volcanic hazards such as volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides are often found around the volcanoes.  Since volcanoes are found along convergent and divergent plate boundaries, these hazards are also generally found along these plate boundaries.  However, not all tectonic hazards are localised. - Other hazards such as tsunamis and volcanic ash may spread beyond the geographic regions where earthquakes and volcanoes are located. - Tsunami waves and volcanic ash may travel thousands of kilometres from where they originated. - Tsunami waves can travel long distances without great loss of energy. Example: The 2004 Indian Ocean tsunami travelled almost 5000km to Africa with sufficient energy to cause deaths and destruction.  Ashfall can travel far from the geographic region where the volcanic eruption occurs. Example: During the eruption of Mount Pinatubo in 1991, ash spread across Southeast Asia. However, whether the dispersal of ash is localised or spreads far beyond the geographic region of the volcano is dependent on wind conditions as well as the volume of ash erupted and the height the ash is thrown into the atmosphere. 2.4 Impact of tectonic hazards on natural and human systems Definitions: Geothermal energy Energy derived from heat from the Earth's crust. Weathering The breaking down or díssolving of rocks and minerals on Earth's surface. Earthquake hazards and their impacts on natural and human systems Earthquake hazard Impact on natural systems Impact on human systems Examples Ground shaking Destroys ecosystems: Ruptures oil and Destroys properties and infrastructures : Weakens buildings, 2010 Haiti earthquake (Mw7.0): Surrounding areas around chemical factories, polluting land and water. bridges, roads and railways, causing them to collapse, factories were polluted. Debris polluted rivers. More than Fractures and uproot trees, causing making it difficult to rescue people or supply emergency aid. 250,000 houses collapsed due to violent vibrations. About widespread tree injury and death and 220,000 people were killed. Water pipes ruptured, causing damaging wildlife habitats. Disrupts services: Snaps water and gas pipes, resulting in water shortages. water shortages and disruptions to gas supply. Electricity and communication cables break, affecting important - 2010 Christchurch, New Zealand earthquakes: Many communication services such as tsunami warnings and trees were damaged and more than 300 had to be television broadcasts. removed, reducing availability of habitats for terrestrial species. Causes injuries and fatalities: People may get trapped under collapsed buildings and infrastructure, resulting in loss of lives and injuries. Soil liquefaction: Liquefaction occurs when Destroys ecosystems: Trees on liquefied soil Destroys properties and infrastructure: Buildings and other 2010 - 2011 Christchurch, New Zealand Earthquakes: Triggered the violent ground shaking causes saturated, sink in and tip over, damaging wildlife infrastructure can sink in and tip over, and the damage severe liquefaction, as the city lies on a former swamp area loose soil to lose its soil structure and habitats, causing forest and biodiversity loss. makes it difficult to rescue people or supply emergency aid. where soils are loose and saturated. More than 60,000 transforms into a thick fluid Liquefied soil may enter rivers and smother residential buildings and infrastructure covering about one-third aquatic plants, causing them to die. Sewage Disrupts services: Electricity and communication cables, and of the city area were damaged. Liquefied soil entered rivers, and pipes may be broken and untreated waste water and gas pipes can sink in and snap, disrupting supply untreated sewage from broken pipes polluted rivers. This materials may pollute rivers, killing aquatic of these services. Roads and railways above liquefied soil resulted in the reduction of some species such as caddisflies. species. can sink in and get damaged, making it difficult to rescue people or supply emergency aid.  Causes injuries and fatalities: People can get trapped under collapsed buildings and infrastructure, resulting in injuries and loss of lives. Landslides: Landslides occur as the violent Destroys ecosystems: Fast-moving debris Destroys properties and infrastructure: Debris can bury 2018 Papua New Guinea earthquake (Mw 7.5): Triggered vibrations: Form cracks on steep slopes, can bury huge areas of forest and wetlands. villages and farms, destroying properties and infrastructure. landslides that caused huge amounts of debris to enter the loosening the rocks and soil Trigger the loose Rivers can be polluted with debris, killing rivers. Caused flooding. Destroyed forests. Polluted waters and rocks and soil to move downslope aquatic life. Rivers can be blocked, causing Disrupts services: Debris can snap electricity and killed fish. floods that can damage nearby ecosystems communication cables, and water and gas pipes, disrupting and properties. supply of these services. Roads and railways can be blocked 2008 Great Sichuan, China Earthquake (Mw 7.9): Triggered more by debris, making it difficult to rescue people or supply than 15,000 landslides. Destroyed many buildings and emergency aid. infrastructure. Caused nearly 20,000 deaths. Causes injuries and fatalities: Debris can bury people or hit them, causing injuries and loss of lives. Debris can block rivers, resulting in floods, which can drown people. Tsunamis: Tsunamis are a series of ocean Destroys ecosystems: The seawater can Destroys properties and infrastructure: Fast moving waters 2004 Indian Ocean Tsunami: Triggered by a 9.1 Mw undersea waves which can be caused by undersea flood huge areas of coastal wetlands and and the large amounts of debris carried in by the waves can earthquake near Sumatra, Indonesia. Tsunami waves slammed earthquakes. Tsunamis can travel over forests, damaging habitats. Large amounts of sweep away buildings and infrastructure, destroying them. into the coasts of 11 Indian Ocean countries, from Indonesia to thousands of kilometres and devastate huge debris carried in by the waves can pollute Somalia in Africa. More than 230,000 people were killed and areas of coastline. these areas, damaging ecosystems and Disrupts services: Fast moving waters and the large amount entire coastlines and habitats were destroyed. killing wildlife. of debris carried in by the eaves can snap electricity and Tsunamis occur when: communication cables, disrupting supply of these services. 2011 Tohoku, Japan earthquake (Mw 9.0): Triggered a tsunami - An undersea earthquake causes the Fast moving water can sweep away roads and railways, up to 40m in height. Waves destroyed homes and seabed to be displaced making it difficult to rescue people or supply emergency aid. infrastructure. Tsunami waves carried debris inland, flooding - A large volume of water is lifted, and polluting large areas of land. Coastal city of Sendai suffered forming waves of great wavelength Causes injuries and fatalities: Sweeping waters can drown extensive damage and half its population was killed. In Iwate, and low height of less than 1 metre. people. Large amounts of debris carried in by the waves can 70,000 pine trees were knocked down, resulting in forest and - The waves travel towards land at high hit and kill people. biodiversity Ioss. The tsunami hit the Pacific islands, speeds around 800km/h. devastating the ecosystems. Entire bird nesting sites were lost, - On approaching the coast, greater and more than 100,000 Layson Albatross Chicks were killed, friction with the shallower seabed and thousands of fish were washed ashore where they slows the waves down. suffocated. - The waves get closer together and increase in height. - Waves can reach up to a height of 15m or more, travel at a speed of 30 - 50km/h and devastate shorelines the waves hit. - Before a tsunami occurs, the sea may recede from the shore because the sea water fills in the void caused by displacement of the seabed. Volcanic eruption hazards and their impact on natural, physical and human systems Volcanic eruption hazards Impact on natural systems Impact on human systems Impact on physical systems Examples Tephra Destroys ecosystems: Ash can be carried Destroys properties and infrastructure: 1991 Mount Pinatubo eruption in the thousands of kilometres by prevailing Volcanic bombs, ranging from a few Philippines: Emitted huge amounts of ash. winds, polluting huge areas of forests, centimeters to the size of vehicles, can hit Buried more than 180km² of forests in ash rivers and other habitats, and destroying properties, damaging them. Ashfall can of about 25cm. Destroyed 800km² of rice ecosystems. Ash can suffocate and kill accumulate on roofs of buildings. When fields, affecting the livelihoods of many wildlife. Ash can cause blindness to birds, saturated with water, the weight of ash farmers. Seven airports in the Philippines with their eyelids getting gummed can double, causing building roofs to had to be closed and many flights were together. collapse. Being corrosive, ash weakens cancelled, disrupting transport. Some building structures, making them more planes were also damaged. likely to collapse. Thick blankets of ash can damage farmland, suffocating crops and destroying livelihoods Disrupts services: Ash particles can damage plane engines, leading to closure of airspaces, and disrupting air transportation services. Causes injuries and fatalities: Volcanic bombs can hit people, causing injuries and loss of lives. Ashfall can cause respiratory problems, eye irritation and suffocate people. Volcanic gases Destroys properties and infrastructure: Destroys ecosystems: Sulfur dioxide Dieng volcano eruption in Indonesia in Sulfur dioxide results in acid rain, which results in acid rain when it reacts with 1979: Released deadly amounts of carbon can corrode buildings and infrastructure. water in the air, which can damage dioxide and killed about 150 people. vegetation, soil and kill wildlife. Cold Threatens public health and cause injuries carbon dioxide is heavier than air, so it can and fatalities: Sulfur dioxide irritates skin, become concentrated in low-lying eyes, nose and throat. Air containing over volcanic areas such as river valleys. Large 3% carbon dioxide can cause headaches amounts of carbon dioxide in the air can and breathing difficulties, and when it kill wildlife, and in the soil, can destroy exceeds 15%, may cause death. vegetation. Lava flows: Lava flows are extremely hot Destroys properties and infrastructure: Destroys ecosystems: Hot, low-silica lava 2018 Kilauea eruption in Hawaii: Far- and can travel over some distances with Lava can burn through homes, properties can travel over some distances, destroying reaching lava flows destroyed more than the geographic region of the volcano. and infrastructure. forests, other habitats and ecosystems in 600 homes. Destroyed huge areas of However, deaths are caused directly by them. forests and ecosystems. Telephone and lava flows are uncommon as people can Disrupts services: Lava can destroy power lines were damaged, causing easily move out of their way. electricity and communication cables, and widespread communication outages. water and gas pipes, disrupting supply of these services. Pyroclastic flows: A pyroclastic flow is a Destroys ecosystems: Huge areas of Destroys properties and infrastructure: 2010 Merapi eruption in Indonesia: Blasted hot cloud of gas, ash, and rocks travelling forests may be destroyed, resulting in The hot flows can burn through all homes,