Chapter 8 - Principles of Environmental Sciences - Geology and Nonrenewable Mineral Resources
ENV 201: Principles of Environmental Sciences - Geology and Nonrenewable Mineral Resources
Instructor: Dr. Abir Hamze
Canadian University of Dubai
Definition of Geology
Geology (from Greek GEO meaning earth and LOGOS meaning discourse)
The science focused on understanding the earth's processes and systems.
Engineering Geology Concerns
Major concerns include:
Rock/Soil Stability
Rock/Soil Deformability Pattern
Geological factors affecting these concerns:
Earthquakes
Volcanoes
Erosions
Groundwater
Slope Stability
Flooding
Classification of Geology
Geology is classified into two broad areas:
Historical Geology
Concerned with the origin and evolution of the Earth, its continents, atmosphere, and life.
Physical Geology
Focuses on rocks, minerals, and the processes affecting them.
Environmental Geology
Environmental Geology:
Discipline studying the effects of geological, climatic, and human-made hazards on the environment to minimize their impact.
Hazards include:
Volcanoes
Earthquakes
Landslides
Floods
Pollution
Geochemistry
Geochemistry:
Science using chemistry principles to explain mechanisms behind geological systems and layers (e.g., Earth's crust and oceans).
Involves identifying the chemical composition of rocks by crushing and analyzing them.
Paleontology
Paleontology:
Branch of geology dealing with former life forms as represented by fossils.
Volcanology
Volcanology:
Science studying the generation and movement of molten rock through volcanoes and volcanic eruptions.
Hydrogeology
Hydrogeology:
Area of geology focusing on the distribution and movement of groundwater in soil and rocks of the Earth’s crust.
Applications include:
Flood prediction and prevention
Water resources management
Earth's Evolution
Origin of the Earth
According to the Big Bang Theory:
A large explosion sent all matter in the universe outward at incredible speeds.
Stars and galaxies formed simultaneously from materials like hydrogen, helium, and heavy metals.
The Earth's story began approximately 13.7 billion years ago with the Big Bang and is related to the Nebular Theory.
Formation of Earth's Layered Structure
Key events in the formation include:
Metals sank to the center, forming the core.
Molten rock and chemical differentiation established the Earth's basic divisions (core, mantle, crust).
A primitive atmosphere evolved from volcanic gases.
Scientific evidence indicates the Earth formed about 4.6 billion years ago.
As it cooled, three major concentric zones were formed: core, mantle, and crust (collectively known as the geosphere).
Earth's Internal Structure
Classification Based on Composition and Properties
Earth's internal layers can be classified by:
Chemical Composition
Physical Properties
Layers are categorized as:
Three Layers:
Crust
Mantle
Core
Five Layers:
Lithosphere (upper mantle)
Mesosphere (lower mantle)
Outer core (liquid)
Inner core (solid)
Asthenosphere (upper mantle)
Core
Core composition:
Inner Core: Hot, solid sphere.
Outer Core: Molten liquid rock.
Mantle
Comprises 82% of Earth’s volume and is 2900 km thick.
Upper mantle is primarily composed of peridotite.
Density: 3.3 g/cm³.
Crust
Comprises two types:
Oceanic Crust:
Homogeneous, dark basalt, 7 km thick, density = 3 g/cm³.
Continental Crust:
Not homogeneous, contains granite (upper crust) and basalt (lower crust), thickness varies between 35-70 km, density = 2.7 g/cm³.
Changes in Internal Properties with Depth
Properties change with depth:
Temperature: Increases with depth.
Pressure: Increases with depth.
Density: Increases with depth as well.
Mechanical strength behaves as follows:
Increases with confining pressure.
Decreases with increasing temperature.
Earth's Spheres
Definition and Importance
Earth is a dynamic body with interconnected parts called spheres:
Hydrosphere:
Water portion of Earth (71% of surface).
Includes oceans (97% of Earth’s water), seas, lakes, ponds, rivers, and streams.
Atmosphere:
Boundary with outer space is the Karman line (100 km above sea level).
90% of the atmosphere is within 16 km of the Earth’s surface.
Composed mainly of Nitrogen (78%) and Oxygen (21%), with minor elements (CO2 at 0.04%).
Biosphere:
Includes all life forms (plants and animals) on Earth.
Geosphere:
The solid Earth, including rocks and minerals.
Accounts for the rock cycle: the process that allows rock types (metamorphic, igneous, sedimentary) to transform into one another.
Minerals
Definitions
Mineral:
Naturally occurring chemical element or inorganic compound that exists as a solid with a repeating atomic arrangement.
Mineral Resource:
Concentration of minerals in Earth's crust that can be extracted and processed into raw materials at an affordable cost.
Formation takes millions of years (thus are nonrenewable resources).
Rocks
Definitions and Types
Rock: Solid combination of one or more minerals.
Types of rocks:
Sedimentary Rocks: Formed from compacted sediments (ex: sandstones, shale).
Igneous Rocks: Formed from cooled magma and lava (ex: granite, lava rock).
Metamorphic Rocks: Altered by high pressure and temperature (ex: slate, marble).
Rock Cycle
Rock Cycle: Interaction of physical and chemical processes changing the Earth’s rocks from one type to another.
Recycling processes include:
Erosion
Melting
Metamorphism
Ore
Ore: Rock with a large concentration of a mineral (often metal), making it profitable for mining.
High-Grade Ore: Contains a high concentration of minerals.
Low-Grade Ore: Contains a low concentration of minerals.
Mineral resources serve various purposes, including providing metallic elements (aluminum, steel, copper, gold) and nonmetallic minerals (sand, gravel, limestone).
Minerals Extraction and Depletion
Overview
Mining nonrenewable mineral resources is constrained by costs associated with finding, extracting, and processing them.
Reserves: Resource deposits that can be profitably extracted; can expand when new sites are discovered or when prices rise.
Depletion Time: Time needed to utilize 80% of resources at a given extraction rate.
Life Cycle of Metal Products
Every metal product undergoes a life cycle involving:
Mining and processing
Manufacturing
Disposal
This cycle consumes energy and water and produces pollution and waste.
Exploitation of Ores
Higher-grade ores are exploited first; mining lower-grade ores requires more resources, leading to land disruption and pollution.
Sustainable Use of Mineral Resources
Strategies to ensure sustainable mineral resource use include:
Recycling and reusing nonrenewable resources (e.g., metals).
Finding substitutes for rare minerals and reusing previously mined minerals (e.g., silicon as a replacement for metals; fiber-optic cables replacing copper and aluminum wires).
Geological Hazards
Types
Major geological hazards include:
Volcanic Eruptions
Earthquakes
Tsunamis
Tectonic Plates
Earth's surface is divided into tectonic plates that move slowly atop the asthenosphere.
Over geological time, these plates have shifted, split apart, and rejoined, causing significant geological forces at their boundaries which lead to:
Mountain formation
Deep valley formation
Earthquakes
Volcanic eruptions
Volcanoes
An active volcano occurs when magma rises in a plume through the lithosphere, reaching the surface via a central vent or fissure.
Molten rock reaching the surface is termed lava.
A volcanic eruption can release:
Chunks of lava rock
Liquid lava
Glowing hot ash
Gases
Earthquakes
Earthquakes occur when stress from forces within the Earth’s mantle causes sudden rock breakage and shifting along a fault or fracture.
This results in the release of accumulated energy as seismic waves, which radiate through surrounding rock.
Measurement of Earthquakes
Most earthquakes are located at tectonic plate boundaries.
The intensity of an earthquake is measured by the magnitude of its seismic waves using the Richter Scale.
Tsunami
Tsunamis: Large waves generated by earthquakes occurring on the ocean floor, where sudden movements of the earth's crust cause rapid changes in the ocean's landscape.