Geography: Geomorphic Hazards, Valuing Landscapes, and Landforms (copy)
Overview of Geomorphic Hazards
Definition of Geomorphic Hazards: These are natural hazards related to the Earth's surface and the processes that shape it. Examples include earthquakes, volcanic eruptions, tsunamis, and ocean trenches.
Plate Tectonics:
Tectonic plates are like jigsaw pieces that move around, forming oceans and continents.
They are in constant motion: colliding (converging), diverging (moving apart), and sliding past each other (transverse).
The movement of these plates is responsible for creating mountains and triggering geomorphic hazards.
The Earth's Layers and Movement:
Lithosphere: This layer contains the Earth's crust and part of the upper mantle. Plate tectonics are part of the lithosphere.
Asthenosphere: Located just below the lithosphere in the hotter upper mantle. It is a viscoelastic solid, meaning it is neither truly liquid nor solid, but moves with a consistency similar to "silly putty" or thick honey.
Convection Currents: These drive plate movement. The hot core heats magma in the mantle, causing it to rise. At the asthenosphere, the magma cools and spreads, pushing the tectonic plates.
Impact: While plate movement is incredibly slow, the force generated has a significant impact on the Earth's surface through geomorphic processes.
Earthquakes
Primary Cause: The movement and interaction of tectonic plates. As plates interact, stress builds up along faults.
Release of Energy: When the stress is released, it travels in the form of seismic waves.
Secondary Causes: Earthquakes can be triggered by volcanic activity, as the movement of magma exerts pressure on surrounding rock formations.
Faults: These are fractures in the Earth's crust where physical movement occurs. Sudden slippage along these faults results in an earthquake.
Volcanoes and Volcanic Activity
Definition: Natural vents in the Earth's crust through which molten rock (magma/lava), gases, and ash are expelled.
Primary Cause of Eruptions: The buildup of pressure within the Earth's mantle forces magma toward the surface.
Location: Activity typically occurs at plate boundaries through processes like subduction or rifting, which lead to the formation of magma chambers. Some occur at hotspots in the middle of plates.
Magma Composition and Gases: The release of gases including water vapor, carbon dioxide (), and sulphur dioxide () contributes to pressure buildup and determines if an eruption is explosive.
Eruption Types:
Effusive: Generally less violent flow of lava.
Explosive: High-pressure release of ash and gas.
Case Study: Kīlauea Volcano, Hawaii
Geographic Uniqueness: Unlike most volcanoes at plate boundaries, the Hawaiian Islands formed in the middle of the Pacific Plate.
Hotspot Theory: A plume of magma (a hotspot) rises from deep within the mantle. As the Pacific Plate moves north-west over this static hotspot, a chain of volcanic islands is created.
Classification: Kīlauea is one of the world's most active shield volcanoes. It has been intermittently erupting since December 23, 2024.
The 2018 Eruption (May 17):
Occurred at the Kīlauea summit at 4:17 a.m.
Ash clouds reached an altitude of feet.
Impacts:
Destroyed over homes.
Displaced approximately to residents.
Sulphur dioxide plumes caused significant respiratory health issues for the population.
Volcanic Risk Management and Mitigation
Mitigation Definition: Implementing strategies to eliminate or minimize the severity of a hazard.
Risk Definition: The probability of a hazard occurring combined with the vulnerability of the population affected.
Monitoring Strategies (USGS Hawaiian Volcano Observatory - HVO):
Thermal cameras.
Gas sensors.
Seismometers (to provide early warnings).
Civic and Government Strategies:
Localised Alerts: Issued by Hawai'i County Civil Defence.
Land-use Planning: Limiting residential development in high-risk lava zones.
Emergency Infrastructure: Traffic restrictions, highway closures, and the creation of physical barriers or trenches to divert lava flows.
USGS Volcano Alert Levels:
Normal: Background, non-eruptive state.
Advisory: Elevated unrest above known background levels.
Watch: Heightened/escalating unrest with increased potential for eruption (timeframe uncertain), or an eruption is underway but poses limited hazards.
Warning: Hazardous eruption is imminent, underway, or suspected.
Valuing Landscapes
Definition of Landscape: The visible features of an area with a consistent character. They can be natural or human (built), and combine living elements with weather/climate-driven changes.
The Four Main Values:
Aesthetic: Based on the attractiveness or beauty of a place. This is subjective and depends on individual backgrounds and opinions.
Economic: Refers to the financial value of the land or its resources (e.g., mining, farming, tourism).
Spiritual: The meaning a place has for identity, religion, or life. This varies by culture and belief system.
Cultural: Expressed through creative means like literature, art, and film. Identity is often shaped by these landforms.
Indigenous Connection to Country: Indigenous Australians have a deep spiritual connection to 'Country.' Landscapes contain sacred places recorded in the 'Dreaming.'
Case Study: Great Barrier Reef (QLD): Valued for its icon status, economic contribution to tourism, and aesthetic beauty.
Case Study: Uluru (NT):
Physical Specs: Stands metres above ground and is kilometres around the base.
Value: Sacred to the Anangu people; features in creation stories (Tjukurpa). It is also a major economic driver, attracting over visitors annually.
Competing Values: Different groups value the same land differently. For example, a mining corporation prioritizes economic value, while Aboriginal communities may prioritize spiritual value. Conflicts are managed through communication, cooperation, and government heritage listings.
Types of Natural Landscapes and Landforms
Mountain Landscapes:
Formed by tectonic plates. Elevated land can reach cold atmospheric heights resulting in snow-capped peaks.
Great Dividing Range: A famous Australian example formed by the crust being forced upwards (fold mountains) on a convergent boundary.
Coastal Landscapes:
The meeting point of land and sea, shaped by wind and waves.
Processes: Erosion (wearing away) and construction (building up).
Australia has over km of coastline and beaches.
Riverine Landscapes:
Formed by the movement of water systems (rivers and surrounding land).
Characterized by rich, fertile land excellent for agriculture.
Arid (Desert) Landscapes:
Defined as receiving less than millimetres of rainfall per year. They cover approximately one-third of the Earth's surface.
Hot Deserts: Located between the Tropic of Capricorn and the Tropic of Cancer (e.g., Sahara, Simpson Desert).
Cold Deserts: Located near the Arctic and Antarctic circles (e.g., Antarctica, Gobi).
Karst Landscapes:
Formed when easily dissolvable bedrock (like limestone) is eroded by slightly acidic water.
Features: Caves, stalactites, springs, and sinkholes (which can be over km deep).
Human Landscapes:
Created by people; defined by infrastructure like buildings, roads, transport, energy, and telecommunications.
Specific Landform Definitions
Coastal:
Atoll: Ring-shaped coral reef encircling a lagoon.
Archipelago: A chain or group of islands.
Spit: Narrow strip of sand protruding into the sea.
Stack: Tall pillar of rock formed by wave erosion.
Mountain:
Cirque: Bowl-shaped hollow formed by glacial erosion.
Ridge: A long, narrow hill-top.
Riverine:
Delta: Fan-shaped deposit area at a river mouth.
Oxbow lake: Crescent-shaped lake on a floodplain.
Arid:
Inselberg: Isolated hill of resistant rock.
Mesa: Flat-topped, steep-sided plateau.
Hamada: Area covered in boulders.
Understanding Contour Maps
Hills: Shown by contour lines forming concentric circles; the smallest circle is the hilltop.
Valleys: Long, low-lying areas. Contours are V or U-shaped with the "point" directed toward high ground; rivers typically flow through them.
Floodplains: Flat land next to rivers. Rivers do not typically flow through contour lines here because the land is so flat.
Spurs: Sloping line of higher ground jutting out from a ridge. Contours (U or V) point away from high ground.
Ridges: Sloping line of high ground. Contours are U or V-shaped.
Escarpments: Sudden change in elevation. Contours are closely packed representing a dramatic drop.
Saddles: A dip or low point between two areas of higher ground; looks like an hourglass on a map.
Cliffs: Vertical or near-vertical features. Contours are extremely close together or touching.
Questions & Discussion
Question: Why would faster-moving plates create more intense hazards?
Response: (Contextual inference from transcript) Faster movement increases the frequency and magnitude of the force generated by plates interacting, leading to higher stress buildup and more violent release of energy.
Question: What does erosion mean?
Response: The process of wearing away the Earth's surface by natural forces like wind and water.
Question: Describe one technique for preventing beach erosion.
Response: (Based on common geographical practice mentioned) Implementing physical structures or management strategies to stabilize the coastline against wave action.
Foundations of Geomorphic Hazards
Definition of Geomorphic Hazards: These are events such as volcanoes, earthquakes, and tsunamis that are primarily caused by tectonic processes, including movements at plate boundaries and activity at hotspots.
Volcanic Eruption Dynamics: The nature of a volcanic eruption is classified as either effusive or explosive. This distinction is determined by the composition and viscosity of the magma. These factors directly influence the level of danger posed to surrounding areas.
Spatial Distribution: Hazards are not distributed evenly across the globe. While the majority are located along tectonic plate boundaries, some occur within the plates themselves at hotspots, with Kĩlauea being a primary example.
Influence of Distribution on Response: The location, accessibility, and level of development of a region affected by a volcano strongly influence the effectiveness of hazard management and response strategies.
Learning Objectives and Essential Questions
Learning Objectives:
Describe the social, economic, and environmental impacts of a specific geomorphic hazard.
Explain the various factors that influence these impacts.
Success Criteria:
Justify which social, cultural, or economic factor exerts the greatest influence on the impacts of a hazard, using evidence to support the claim.
Essential Question (EQ): What influences the severity of impacts from a geomorphic hazard?
The Disaster Risk Equation
Concept Definition: The disaster risk equation is used to illustrate the likelihood of a disaster occurring based on several intersecting factors.
Mathematical Formula:
Analysis of the Formula:
If a country possesses high vulnerability and a low capacity to cope, even a moderate hazard will result in a high disaster risk.
To decrease disaster risk, countries must increase their capacity to cope. This is achieved through robust response systems, superior infrastructure, and the implementation of mitigation strategies.
Discussion Question (Think / Pair / Share): Could a wealthy country still have high vulnerability?
Factors Influencing Hazard Impacts
Social, cultural, and economic factors dictate a community’s level of vulnerability and its capacity to cope with geomorphic events. These factors influence where people choose to live, how they perceive risk, and whether they have the necessary resources to prepare for, survive, and recover from disasters.
Social Factors:
Population Density.
Education levels.
Health Care quality and access.
Population demographics (age, gender, etc.).
Economic Factors:
Wealth (GDP and individual income).
Infrastructure quality.
Access to Technology.
Emergency Services availability.
Cultural Factors:
Beliefs and Traditions.
Attitudes toward risk.
Indigenous Knowledge.
Community Cooperation.
Case Study: Social Influence – 2010 Haiti Earthquake
Event Details: On January , an earthquake measuring a magnitude of struck near the capital city, Port-au-Prince.
Sequence of Events: The initial strike was followed shortly by two significant aftershocks with magnitudes of and .
Impact on Human Life: Death toll estimates vary depending on the source:
General estimates range from to .
Haitian government figures estimate deaths between and .
Impact on Infrastructure: The Haitian government estimated that residences and commercial buildings either collapsed or sustained severe damage.
The Role of Population Density:
Port-au-Prince had an approximate density of people per .
This high density significantly contributed to the high death toll.
Comparative Population Densities (People per ):
Perth:
London:
Tokyo:
Case Study: Economic Influence – 2011 TŁhoku Earthquake and Tsunami
Event Details: On March , an earthquake measuring magnitude and a subsequent tsunami struck Japan.
Economic Context: Japan is one of the world’s wealthiest and most highly developed countries. Consequently, economic factors were central in shaping the impacts and the recovery.
Mitigation and Investment:
Japan has made substantial investments in seismic engineering and earthquake building technology.
The country employs strict building codes and sophisticated warning systems to minimize damage.
Resilience and Self-Financing:
Wealth allows Japan to self-finance major disaster mitigation and rapid economic recovery strategies.
This reduces reliance on international aid and allows their highly developed society to absorb shocks and rebuild with remarkable speed.
Case Study: Cultural Influence – 2004 Indian Ocean Tsunami
Event Details: On December , a magnitude earthquake occurred off the west coast of Sumatra, Indonesia, triggering a massive tsunami.
General Impact: The tsunami caused widespread fatalities, injuries, and displacement across Asia, destroying homes, livelihoods, and coastal infrastructure.
Contrast in Outcomes on Simeulue Island:
While over people were killed across the region, only seven people died on Simeulue Island out of a population of approximately . This is despite the island being located only from the earthquake's epicenter.
Traditional Knowledge – "Smong":
The residents of Simeulue used a traditional warning system known as smong, which is preserved in local songs and stories.
"Smong" describes a specific sequence: the earthquake occurs, the sea recedes, and then a giant wave arrives.
This knowledge was established following a tsunami in and passed down through oral traditions.
Recognizing these ancestral signs, the population immediately fled to higher ground, which resulted in the survival of nearly the entire island population.
Independent Practice and Vocabulary
Key Vocabulary:
GDP per capita: A measure of a country's economic output per person.
Task – Hazard Comparison Analysis:
Describe how access to healthcare influences hazard impacts.
Describe how GDP per capita influences the impacts of earthquakes.
Conduct a PQE analysis to describe the relationship between wealth and hazard impacts.
Investigate the cultural factors that influenced impacts in Christchurch and Haiti, assessing the level of influence these factors had.
Summary of Findings
Vulnerability to geomorphic hazards is dictated by the intersection of social, cultural, and economic factors.
Economic strength (wealth, infrastructure, building standards, and emergency services) is a primary driver in reducing death tolls and accelerating recovery times.
Social and cultural assets (education, community cooperation, and traditional/indigenous knowledge) improve the immediate response of individuals to hazards, directly saving lives.