Geophysical hazards Flashcards
What is a hazard event?
The occurrence of a hazard.
What is a disaster?
A major hazard that impacts a populated area.
What is risk?
The probability of a hazard event.
What is vulnerability?
The geographic conditions that increase the chances of a disaster.
What is hazard perception?
The degree to which a hazard is considered to be a threat by different people.
What is a secondary hazard?
The effect or occurrence of a second hazard following the primary hazard.
What is resilience?
The ability to save lives and infrastructures.
What is adaptation?
Ways human actions have changed to alter the chances of a disaster.
What are the layers of Earth’s structure?
Lithosphere (crust and uppermost mantle), asthenosphere, upper mantle, lower mantle, core (outer and inner).
What is the crust broken into?
Tectonic plates.
What are the types of tectonic plate movements?
Constructive, transformative, and destructive.
What is constructive plate movement?
Plates move apart from one another, creating a rifting zone where magma rises and new land is formed.
What is transformative plate movement?
Plates move sideways, creating a fault.
What is destructive plate movement?
Plates move towards one another, creating a destructive zone and subduction zone when one of the plates goes under into the uppermost mantle.
What are the types of destructive plate movement?
- Oceanic - continental, oceanic goes down since it is denser. 2. Oceanic - oceanic. 3. Continental - continental.
What is the theory of tectonic plate movement?
Ridge push and slab pull.
What are hot spots?
The places where magma escapes through the crust, far from plate boundaries.
What is a volcano?
It is where magma erupts onto Earth’s surface through a vent in the crust
What are the three types of volcanoes?
Composite, Cinder and Shield
Describe a composite volcano
It is typically a tall cone shaped mountain, its surface is made of alternating layers of ash and lava. Its eruptions are normally explosive with sticky viscous lava. it is normally found in destructive plate boundaries
Describe a shield volcano
It is gently sloped, with gentle eruptions of thin, runny lava, it is normally found in constructive plate boundaries
Describe a cinder volcano
It is typically short, it has a bowl shaped crater. Most eruptions are pyroclastic products or cooled lava
What are the secondary hazards to volcanoes?
Lahars, landslides and pyroclastic flow
Describe the secondary hazards of volcanoes
Lahars are mudflows, tephra mixed with water or snow, it is very destructive and can go on for many kms. Landslides is mass movement downwards due tp gravity or crust movement and pyroclastic flow is the deadliest secondary hazard since its a warm mixture of gas and tephra (lahars and pyroclastic flows are most commonly found in composite volcanoes)
The index of Volcanic activity
VEI, Volcanic Eruption Index
