NOTE: NO DIAGRAMS ON EXAM AND NOT ASKED TO DRAW ANY, BUT CAN BE
ASKED INFO FROM ANY DIAGRAM
WEEK 1 – INTRO TO HAZARDS
Hazards
- In an average year, hazards require over 20 million people around the
world to evacuate their homes.
- Within North America, every location is at risk from at least one
hazardous process
- Examples
o West coast: earthquakes, landslides
o East coast: hurricanes
o Mid-continent: tornadoes, blizzards
o All areas: drought
- Some hazards pose a risk to both humans and the environment.
- Examples:
o Nuclear meltdowns
o Toxic gas release
o Oil spills
o Ozone depletion
o Acid rain
o Infrastructure failure (bridge collapses)
o Shipwrecks
o Airplane crashes
Processes and Natural Hazards
- Natural hazards can arise from three main processes:
1) Internal forces within the Earth
a. Driven by the internal energy of the Earth (ex. Plate
tectonics)
2) External forces on Earth’s surface
a. Driven by the sun’s energy
b. Ex. Atmospheric effects
3) Gravitational attraction
a. Driven by the force of gravity
b. Ex. Downslope movement
Definitions:
- Hazard – a process that poses a potential threat to people or the
environment
- Risk – the probability of an event occurring multiplied by the impact
on people or the environment
, - Disaster – a brief event that causes great property damage or loss of
life
o Carrying out of a hazard (actually occurs)
- Catastrophe – a massive disaster
Hazards as Potential Catastrophes
- Hazards differ in their potential to cause a catastrophe based on the
size of the area affected.
- More likely to be catastrophic: Tsunamis, earthquakes, volcanoes,
hurricanes, floods
- Less likely to be catastrophic: landslides, avalanches, wildfires,
tornadoes
Magnitude and Frequency
- The impact of a hazard is a function (relationship) of both its
magnitude (i.e. energy released) and frequency.
- It can also be affected by other factors (geology, land use, population
density, etc.)
- * Magnitude-Frequency Concept
o There is an inverse relationship between magnitude and
frequency
o High magnitude events have low frequency
Understanding the Risk of Hazards
- The history of an area can provide insight on
its risk of hazards.
- The following provide clues:
o maps, historic documents, journals,
aerial photos (big for landslides)
o Weather and climate data
o Craters, faults, valleys
The Geologic Cycle
- Throughout Earth’s 4.6-billion-year history, the materials on or near
the surface have been created and modified by physical and chemical
processes.
- Collectively, these processes are called the geologic cycle, which
encompasses the following:
o Tectonic cycle
o Rock cycle
, o Hydrologic cycle
The Tectonic Cycle
- This cycle involves the creation, movement, and destruction of
tectonic plates.
- Tectonic plates: large blocks of the Earth’s crust that form its outer
shell; there are 14 plates
- New land is formed at mid-ocean ridges and land is destroyed at
subduction (sinking) zones
- The process is driven by Earth’s internal energy
Earth’s Internal Structure
- The inner core is extremely hot and solid.
- The asthenosphere (upper mantle) is composed of
hot magma with some flow
- The lithosphere is a thin and brittle (cracks and
breaks from the plates) crust
Plate Tectonics
- The crust forms the upper part of the lithosphere
and is broken into fragments (plates).
- Two types of crust:
o Oceanic: dense, thin (averages 7km
thickness)
o Continental: relatively buoyant, thick
(averages 30km thickness)
- Movement of the plates is caused by convection
currents within the mantle
- Plate boundaries do not tend to match up with the
boundaries of continents or oceans.
- The movement of plates causes dynamic events on Earth’s surface,
especially at plate boundaries
- * Types of plate boundaries:
o Divergent
o Convergent
o Transform
Plate Boundaries
-
, Plate Tectonics
- The continents of today were clustered into the supercontinent of
Pangaea 250 million years ago.
- Evidence for this includes current mountain ranges and fossils
Divergent Plate Boundaries
- At these boundaries, plates move away from each
other.
- New land is created at these locations.
- Divergence results in seafloor spreading and
causes oceanic ridges to form (ex. Mid-Atlantic
Ridge)
- The Atlantic Ocean is getting wider by a few cm
every year.
Convergent Plate Boundaries
- At these boundaries, plates move toward each other.
- Collisions involving oceanic and continental crust result in subduction
zones:
o Dense ocean plates sink and melt
o The melted magma rises to form mountains and volcanoes (ex.
Andes)
- Collisions involving two continental plates result in collision
boundaries:
o Neither plate sinks
o Tall mountains tend to form (ex. Himalayas)
Subduction Zones Collision Boundaries
ASKED INFO FROM ANY DIAGRAM
WEEK 1 – INTRO TO HAZARDS
Hazards
- In an average year, hazards require over 20 million people around the
world to evacuate their homes.
- Within North America, every location is at risk from at least one
hazardous process
- Examples
o West coast: earthquakes, landslides
o East coast: hurricanes
o Mid-continent: tornadoes, blizzards
o All areas: drought
- Some hazards pose a risk to both humans and the environment.
- Examples:
o Nuclear meltdowns
o Toxic gas release
o Oil spills
o Ozone depletion
o Acid rain
o Infrastructure failure (bridge collapses)
o Shipwrecks
o Airplane crashes
Processes and Natural Hazards
- Natural hazards can arise from three main processes:
1) Internal forces within the Earth
a. Driven by the internal energy of the Earth (ex. Plate
tectonics)
2) External forces on Earth’s surface
a. Driven by the sun’s energy
b. Ex. Atmospheric effects
3) Gravitational attraction
a. Driven by the force of gravity
b. Ex. Downslope movement
Definitions:
- Hazard – a process that poses a potential threat to people or the
environment
- Risk – the probability of an event occurring multiplied by the impact
on people or the environment
, - Disaster – a brief event that causes great property damage or loss of
life
o Carrying out of a hazard (actually occurs)
- Catastrophe – a massive disaster
Hazards as Potential Catastrophes
- Hazards differ in their potential to cause a catastrophe based on the
size of the area affected.
- More likely to be catastrophic: Tsunamis, earthquakes, volcanoes,
hurricanes, floods
- Less likely to be catastrophic: landslides, avalanches, wildfires,
tornadoes
Magnitude and Frequency
- The impact of a hazard is a function (relationship) of both its
magnitude (i.e. energy released) and frequency.
- It can also be affected by other factors (geology, land use, population
density, etc.)
- * Magnitude-Frequency Concept
o There is an inverse relationship between magnitude and
frequency
o High magnitude events have low frequency
Understanding the Risk of Hazards
- The history of an area can provide insight on
its risk of hazards.
- The following provide clues:
o maps, historic documents, journals,
aerial photos (big for landslides)
o Weather and climate data
o Craters, faults, valleys
The Geologic Cycle
- Throughout Earth’s 4.6-billion-year history, the materials on or near
the surface have been created and modified by physical and chemical
processes.
- Collectively, these processes are called the geologic cycle, which
encompasses the following:
o Tectonic cycle
o Rock cycle
, o Hydrologic cycle
The Tectonic Cycle
- This cycle involves the creation, movement, and destruction of
tectonic plates.
- Tectonic plates: large blocks of the Earth’s crust that form its outer
shell; there are 14 plates
- New land is formed at mid-ocean ridges and land is destroyed at
subduction (sinking) zones
- The process is driven by Earth’s internal energy
Earth’s Internal Structure
- The inner core is extremely hot and solid.
- The asthenosphere (upper mantle) is composed of
hot magma with some flow
- The lithosphere is a thin and brittle (cracks and
breaks from the plates) crust
Plate Tectonics
- The crust forms the upper part of the lithosphere
and is broken into fragments (plates).
- Two types of crust:
o Oceanic: dense, thin (averages 7km
thickness)
o Continental: relatively buoyant, thick
(averages 30km thickness)
- Movement of the plates is caused by convection
currents within the mantle
- Plate boundaries do not tend to match up with the
boundaries of continents or oceans.
- The movement of plates causes dynamic events on Earth’s surface,
especially at plate boundaries
- * Types of plate boundaries:
o Divergent
o Convergent
o Transform
Plate Boundaries
-
, Plate Tectonics
- The continents of today were clustered into the supercontinent of
Pangaea 250 million years ago.
- Evidence for this includes current mountain ranges and fossils
Divergent Plate Boundaries
- At these boundaries, plates move away from each
other.
- New land is created at these locations.
- Divergence results in seafloor spreading and
causes oceanic ridges to form (ex. Mid-Atlantic
Ridge)
- The Atlantic Ocean is getting wider by a few cm
every year.
Convergent Plate Boundaries
- At these boundaries, plates move toward each other.
- Collisions involving oceanic and continental crust result in subduction
zones:
o Dense ocean plates sink and melt
o The melted magma rises to form mountains and volcanoes (ex.
Andes)
- Collisions involving two continental plates result in collision
boundaries:
o Neither plate sinks
o Tall mountains tend to form (ex. Himalayas)
Subduction Zones Collision Boundaries
