ERTH2404 Lecture Notes Review

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ERTH2404 Lecture 11: Overview

Topics Covered

  - a) Permafrost
  - b) Groundwater
  - c) Earth Resources
  - Instructor: Maurice Lamontagne

Section 1: Permafrost

Learning Objectives

  - Recognizing permafrost in Canada’s North and mountainous regions, including associated hazards.
  - Engineering solutions to manage permafrost.

Definition of Permafrost

  - Permafrost: Ground (soil or rock, including underwater sediments) that remains at a temperature of 0°C or lower for at least two consecutive years.
    - Permanently frozen ground comprising soils and rock.
    - Definition is based solely on temperature, irrespective of composition, texture, or water content.
    - Continuous permafrost grades from deep (1000 m) in the North to thin (30 cm) in southern regions.

Extent of Permafrost

  - Underlies 20% of the Earth's land surface; comprises 50% of Canada's territory.
  - Types of permafrost in Canada:
    - Continuous, Discontinuous, Sporadic, Isolated, Subsea.

Permafrost in Canada

  - Approximately 50% of Canada's territory covered by permafrost, categorized into various types and regions.

Changes in Permafrost

  - Permafrost characteristics are dictated by the energy balance at the surface (energy received vs. energy lost).
    - Influencing factors include:
      - Warming climate
      - Deeper snow cover
      - Surface disturbance (e.g., human activities)
    - Results in thawing of the active layer and potentially complete loss of permafrost over time.
    - Ground ice thawing can lead to thermokarst processes, which include subsidence and landsliding.

Engineering Considerations

  - Unwanted thawing under structures can compromise soil strength.
    - Results:
      - Subsidence
      - Liquefaction and slope instability
      - Frost heave: Uplift caused by freeze-thaw cycles.
  - Examples of engineering adaptations:
    - Elevated systems for pipelines, buildings, and roads to mitigate heat transfer to permafrost.

Mitigation Strategies

  - Build roads and railways with insulating layers.
  - Utilize artificial ground freezing for engineering structures, such as tunnels and shafts.

Section 2: Groundwater

Learning Objectives

  - Understanding groundwater flow as per Darcy’s Law.
  - Familiarity with zones of subsurface water: aquifers, aquitards, water tables, etc.
  - Concepts related to drinking water, well construction, and water quality.

Hydrologic Cycle

  - Describes the constant exchange of water between oceans, atmosphere, and continents, operational for over 4 billion years.
  - Hydrosphere: Totality of Earth's water, in both liquid and solid states, fresh and saline.

Statistics and Definitions

  - Total volume of water on Earth: 1.36 billion km³
    - 97.20% is seawater
    - 2.15% is glacial ice
    - 0.62% is groundwater (20 times the volume of lakes, rivers, etc.)
    - 0.03% is other freshwater bodies (lakes, rivers, etc.).

Importance of Groundwater

  - Groundwater is the largest readily available reservoir of fresh water for human use (94% of available fresh water, excluding glaciers).
  - Groundwater serves domestic, agricultural, and industrial needs.

Zones of Subsurface Water

  - Unsaturated Zone: Near-surface soil moisture containing both air and water, also called the vadose zone.
    - Capillary Fringe: Water held by surface tension near the water table.
  - Saturated Zone: All pore spaces in rocks or soils filled with water.
  - Water Table: Upper limit of the saturated zone; where water pressure equals atmospheric pressure.

Recharge and Discharge

  - Water is transferred from areas with higher water table (recharge areas) to lower (discharge areas).
  - Seasonal and annual depth variations occur in the water table based on topography.

Springs

  - Spring: Localized discharge points where the water table intersects the Earth's surface.

Section 3: Earth Resources

Overview

  - Categories of Earth resources include:
    - Non-metallic
    - Metallic
    - Energy resources (Fossil Fuels + Uranium)

Mineral Resources Use

  - 94% of all mineral resources are non-metallic.
  - Examples of non-metallic minerals: limestone, clay minerals, potash, gypsum.

Challenges in Resource Extraction

  - Resource exploration involves understanding geological environments that create ore deposits.
  - Exploration methods: Geophysics, field work, drilling, geological mapping.

Fossil Fuels

  - Types of fossil fuels include coal, oil, and natural gas; created from organic matter subjected to heat and pressure.
  - Oil sands are a significant Canadian resource requiring specific extraction methods.

Uranium Mining

  - Canada ranks as the third-largest producer of uranium, primarily for nuclear energy.

Environmental Impact

  - Challenges include managing waste materials and potential contamination of resources.