Unit 9 Flashcards
Where and how do volcanic eruptions occur?
Original Answer: Volcanic eruptions occur at three main tectonic settings: divergent boundaries, where magma rises as plates move apart (e.g., mid-ocean ridges like Iceland); convergent boundaries, where subduction of one plate forces magma upward (e.g., Pacific Ring of Fire); and hot spots, where plumes of magma rise through the Earth’s crust away from plate boundaries (e.g., Hawaii).
Simple Terms: Volcanic eruptions happen where magma escapes to the surface. This occurs at divergent boundaries (where plates move apart, e.g., mid-ocean ridges), convergent boundaries (where one plate goes under another, e.g., Pacific Ring of Fire), and hot spots (where magma rises in the middle of a plate, e.g., Hawaii).
Why may volcanic eruptions be hazardous?
Original Answer: Volcanic eruptions are hazardous due to their ability to produce pyroclastic flows (fast-moving hot gases and volcanic materials), lava flows that destroy infrastructure, lahars (mudflows), widespread ash clouds that disrupt air travel and agriculture, and gas emissions (e.g., sulfur dioxide) that harm health and the environment.
Simple Terms: Volcanic eruptions are dangerous because they can release fast-moving hot gases and ash (pyroclastic flows), rivers of lava, mudflows (lahars), ash clouds that disrupt life and farming, and toxic gases that harm health.
Why might it be possible to predict a volcanic eruption more easily than an earthquake?
Original Answer: Volcanic eruptions may be easier to predict because they are often preceded by detectable warning signs such as increased seismic activity, gas emissions (e.g., sulfur dioxide), ground deformation (monitored by GPS), and rising magma temperature. Earthquakes, however, usually occur without clear or long-term precursors.
Simple Terms: Volcanic eruptions are easier to predict because scientists can monitor warning signs like increased earthquakes near a volcano, changes in gas levels, swelling of the ground, and rising magma heat. Earthquakes don’t usually have such clear warnings.
Why do earthquakes or volcanic eruptions have greater impacts in some areas than in others?
Original Answer: The impacts are influenced by factors such as population density (higher populations result in more casualties and damage), building quality (poorly constructed buildings are more vulnerable), proximity to the hazard (closer to the epicenter or volcano increases risks), and preparedness (developed countries often have better emergency plans).
Simple Terms: The impact depends on how many people live in the area (population density), how strong and safe the buildings are, how close the hazard is, and how prepared the community is for emergencies. Poorer areas are often affected worse.
To what extent can volcanic eruptions be predicted and their hazardous effects limited?
Original Answer: Volcanic eruptions can often be predicted using monitoring techniques like detecting seismic activity, changes in gas emissions, and ground deformation. However, predictions are not always precise. Hazardous effects can be limited through measures like establishing exclusion zones, emergency evacuations, public education, and early warning systems.
Simple Terms: Scientists can often predict eruptions by watching for warning signs like small earthquakes, gas release, and ground swelling. Damage can be reduced by evacuating people, keeping people away from danger zones, and having good emergency plans.
What factors determine the nature of volcanic eruptions?
Original Answer: The nature of volcanic eruptions depends on magma composition (silica-rich magma is more viscous and explosive), viscosity (higher viscosity traps gases, leading to explosive eruptions), gas content (more gas increases eruption violence), and water presence (subducted water increases explosive potential). Effusive eruptions occur with low-viscosity magma, while explosive eruptions involve high-viscosity magma.
Simple Terms: The type of eruption depends on the magma. Thick, sticky magma traps gases and causes explosive eruptions. Runny magma lets gases escape easily, causing gentle eruptions. Water and gas in the magma can also make eruptions more violent.
How is the distribution of volcanic hot spots different from other types of volcanoes?
Original Answer: Volcanic hot spots occur within tectonic plates, often far from plate boundaries, due to rising plumes of magma from deep in the mantle (e.g., Hawaii, Yellowstone). Other volcanoes are mostly located along plate boundaries, such as subduction zones (e.g., Andes) and divergent boundaries (e.g., mid-ocean ridges).
Simple Terms: Hot spots are in the middle of tectonic plates, caused by magma rising from deep inside the Earth (e.g., Hawaii). Other volcanoes are mostly found along plate boundaries where plates move together, apart, or slide past each other.
What are the causes and distribution of earthquakes?
Original Answer: Earthquakes are caused by the sudden release of energy along faults due to tectonic plate movement. This includes divergence (plates moving apart), convergence (plates colliding or subducting), and transform boundaries (plates sliding past each other). They are concentrated along tectonic plate margins, such as the Pacific Ring of Fire and the Himalayan region.
Simple Terms: Earthquakes happen when the ground suddenly shakes due to plates moving. They occur at boundaries where plates collide, pull apart, or slide past each other. Most earthquakes are found along tectonic plate margins, like the Pacific Ring of Fire.
What are the causes and hazardous effects of tsunamis?
Original Answer: Tsunamis are caused by underwater disturbances like earthquakes, volcanic eruptions, or landslides that displace large amounts of water. Their hazardous effects include massive coastal flooding, destruction of property and infrastructure, loss of life, contamination of water supplies, and long-term economic and environmental damage.
Simple Terms: Tsunamis are caused by underwater earthquakes, volcanoes, or landslides that push water up into big waves. They cause flooding, destroy buildings, kill people, and damage the environment.
To what extent can mass movements on slopes be seen as the result of human activities?
Original Answer: Mass movements can often be attributed to human activities that destabilize slopes. These include deforestation (removing vegetation that stabilizes soil), mining (weakening slope structure), construction (overloading slopes with weight), and agriculture (removing surface cover and altering natural drainage). Human-induced climate change can also increase rainfall intensity, further exacerbating slope instability.
Simple Answer: Human actions like cutting trees, building, farming, and mining can weaken slopes and cause mass movements.
Under what circumstances can sudden mass movements occur and become hazardous?
Original Answer: Sudden mass movements can occur when slopes become unstable due to natural or human-induced triggers. These include heavy rainfall saturating soil, earthquakes causing ground shaking, volcanic activity loosening material, rapid snowmelt, or anthropogenic factors like construction or excavation. Hazards arise from the speed and volume of material moving, which can cause destruction, bury infrastructure, and threaten lives.
Simple Answer: Sudden mass movements happen when heavy rain, earthquakes, or human actions like digging make slopes unstable, leading to fast and dangerous material movement.
What measures can be taken to limit the hazardous effects of mass movements?
Original Answer: Measures include stabilizing slopes through engineering (e.g., retaining walls, terracing, or rock bolting), replanting vegetation to anchor soil, improving drainage to prevent water buildup, installing monitoring and early warning systems, and implementing land-use policies to restrict construction in high-risk areas. Community education and awareness programs can also improve preparedness and response.
Simple Answer: To reduce risks, we can strengthen slopes, plant trees, improve drainage, monitor danger, and avoid building in risky areas.
What conditions allow a hurricane (tropical storm) to become a major hazard?
Original Answer: Hurricanes become major hazards when warm ocean temperatures (≥27°C) provide energy for intense convection, low wind shear allows storm structure to develop, humid air feeds further intensification, and a pre-existing weather disturbance triggers cyclonic activity. These factors produce high wind speeds, heavy rainfall, storm surges, and flooding.
Simple Terms: Hurricanes need warm ocean water (≥27°C), low wind interference, humid air, and a weather disturbance to start. These create strong winds, heavy rain, flooding, and storm surges.
How can the development and path of a hurricane (tropical storm) be predicted?
Original Answer: The development and path of hurricanes can be predicted using satellite imagery to track cloud patterns and sea surface temperatures, computer models to simulate storm movement, and weather buoys for real-time data collection. Accurate monitoring of atmospheric conditions, such as wind shear and pressure systems, also aids in forecasting.
Simple Terms: Scientists use satellites, computer models, and weather data to track storms. They study cloud patterns, ocean temperatures, wind conditions, and pressure to predict where the storm will go.
What are ways to mitigate the damage and loss of life caused by hurricanes (tropical storms)?
Original Answer: Damage and loss of life can be mitigated through early warning systems to alert communities, evacuation plans to move people from high-risk areas, construction of storm-resistant buildings and flood defenses, proper land-use planning to avoid vulnerable zones, and community education about disaster preparedness.
Simple Terms: We can reduce harm by warning people early, evacuating areas at risk, building stronger structures, improving land use to avoid flood zones, and teaching people how to stay safe.
