Paper 1) Hazardous Environments Flashcards
Hazard definition
A natural hazard is a natural events that have the potential to harm people and their property.
Disaster definition
A major hazard event that causes widespread disruption to a community or region, with significant demographic, economic and/or environmental losses, and which the affected community is unable to deal with adequately without outside help.
What is one of the least hazardous places in the world?
-Central Russia
-landlocked - no tropical cyclones
-no active volcanoes present
-low frequency and intensity of tornadoes
-high continentality - no risk from storm surges or tsunamis
What is one of the most hazardous places in the world?
-Philippines
-Country most exposed to tropical storms in the world
-located near the Ring of Fire - prone to earthquakes
-other hazards - typhoons, landslides, floods
Earth’s structure
Crust - the thinnest layer:
-oceanic crust - under the sea - denser, made of basaltic rock
-continental crust - under the land - lighter, granitic rock
Mantel - thickest layer:
-upper: lithosphere, asthenosphere
-lower
Core - 5000C
-inner - liquid iron and nickel
-outer - solid ball of iron and nickel
Convection current
The core heats the magma and it rises. As it rises and cools, it solidifies and sinks down again. The core heats it up again and the cycle restarts.
Ring of fire
-region where many volcanoes and earthquakes take place
-along the rim of the Pacific ocean, near the Philippines, Japan, Mexico, etc.
-home to 452 volcanoes
-75% of the world’s largest earthquakes are found along it
-Japan has 10% of the world’s active volcanoes and has 15 volcanic events every year
Evidence for plate tectonic theory
-continental fit
-biological evidence
-tectonic activity
-geological evidence
Evidence of plate tectonic theory - continental fit
-the matching of large-scale geological features on different continents.
-the coastlines of South America and West Africa seem to match up
Evidence of plate tectonic theory - biological evidence
Many fossils found along the edges of different continents are the same, which suggests that the two continents were joined at some point in the past
Evidence of plate tectonic theory - tectonic activity
There is a large amount of seismic, volcanic, and geothermal activity along the plate boundaries, which defines them clearly.
Evidence of plate tectonic theory - geological evidence
Mountain ranges that link across continents
-Ridges, e.g. mid-Atlantic ridge where plates are separating (sea floor spreading) - produced by lava welling up from between the plates as they pull apart (sea floor spreading)
Types of plate boundaries
-constructive/ divergent
-destructive
-conservative
-convergent
Constructive plate boundary
-also divergent plate boundary
-two plates moving apart from each other
-e.g. Mid Atlantic Ridge - located along the floors of the Atlantic Ocean. Lava wells up from between the plates as they pull apart and solidifies
Earthquakes:
-caused by friction as the plates tear apart
-low magnitude, do not cause damage
-forms shield volcanoes
Destructive plate boundary
-continental plate meeting a oceanic plate
-oceanic plate is denser than the continental plate as they are moved together
-the oceanic plate is forced underneath the continental plate
-Earthquakes - as the oceanic plate submerges under the continental plate - subduction zone - friction builds up
-Volcanoes - the magma collects to form a magma chamber, then rises up through cracks in the continental crust. As the pressure builds up, a volcanic eruption may occur
-Peru-Chile Trench
Conservative plate boundary
-where two plates slide past each other in the opposite or in the same direction but at different speeds
-no volcanic activity
-earthquakes - plates do not pass each other smoothly, the friction between the two plates causes resistance. Pressure builds, the crust can fracture, releasing energy as earthquakes
-e.g. San Andreas fault
Convergent plate boundary
-when two continental plates or two oceanic plates move together and meet
-collision zones
-when two ocean plates move towards each other, layers of sedimentary rock on the sea floor become folded
-eventually, the sedimentary rock appear above sea level as a range of fold mountains
-e.g. The Himalayas - fold mountains
Two types of volcanoes
-composite volcano
-shield volcano
Composite volcano
-usually found at destructive boundaries
-violent, explosive eruptions
-made of alternating ash and lava
-steep slopes as lava is less viscous -pyroclastic flow rather than a lava flow
Shield volcano
-usually found at constructive plate boundaries
-formed by eruptions of thin, runny lava
-eruptions are more frequent but relatively gentle
-gentle slope
-low, wide cone
Super volcanoes
-a volcanic center that has had an eruption of magnitude 8 on the Volcano Explosivity Index (VEI)
-At one point in time it erupted more than 1,000 cubic kilometers (240 cubic miles) of material
Hotspot theory
-volcanoes can be formed away from plate boundaries - hotspots
-caused by weak spots in the crust
-formed by plumes of superheated rock rising very slowly through the mantle, causes the asthenosphere and the lithosphere to melt
-magma rises through weaknesses in the crust and erupts at the earth’s surface
-oceanic hotspots - erupts basaltic lava, huge shield volcanoes
-continental hotspots - viscous, granitic lava, erupts explosively
Causes of earthquakes
Sudden violent shaking of the ground
-plates try to move and become stuck
-pressure builds up because the plates are still trying to move
-when the pressure it released, it sends out huge amounts of energy causing the Earth’s surface to shake violently
Focus definition - earthquake
The point inside the Earth’s crust where the earthquake originates from
Seismic waves definition
-the earthquake’s energy that is released and spread out from the focus
Epicentre definition
Point on the Earth’s surface directly above the focus
Richter scale
-a numerical scale for expressing the magnitude of an earthquake from seismograph oscillations
-10 point scale
-Logarithmic
Mercalli scale
-measures how much damage is caused by the earthquake based on observations
-scale between 1-12
-perception made from observer and the estimation they make based on damage to surroundings
Magnitude vs intensity definition
-The great size or extent of something (earthquakes). Used for the Richter Scale
-Describing the severity of an earthquake in number form. Used for the Mercalli Scale
Advantage of the Richter scale over the Mercalli scale
-Richter scale shows an accurate magnitude no matter the location
-Mercalli scale bases the earthquake’s intensity on the damage done to the surroundings
-if an earthquake is the same magnitude, but at an inhabited or uninhabited area, it is different
-it is objective as it is based on the perception of the onlooker
Seismograph
Used to detect and record the vibration of the earth surface. Its vibrations are shown on display or paper print.
Three actions that can be taken to reduce the impact of earthquakes
-Predict - difficult, but can observe the swelling of the rock, bubbles and gases coming to the surface, notice seismograph to tell if there are shocks and notice animal behaviours
-Protect - design and build structures that are safe and provide protection
-Prepare - authorities - e.g. for evacuation, training emergency services, putting warning systems in place, preparing hospitals, food supply, educating people
Three parts that make up a emergency disaster plan
- Prepare the area for disaster
- Try to save people’s lives and look after the people worst affected
- Aim to get the area back to normal again
What can people do with a few seconds warning
-try to evacuate the building
-look for somewhere safe to go
-Tsunami - get to high ground
-find a place to drop, cover, hold
Remote sensing and GIS
-Remote sensing is the science of obtaining information about objects or areas from a distance, typically from aircraft or satellites.
-Satellite images are increasingly being used.
-Image of the affected area immediately after the earthquake can provide valuable information for search and rescue operations.
-GIS - a computer system that consists of software used to analyze the collected data and hardware that the software would operate in