Environmental Geology Study Notes

SCI250 - Environmental Geology

Introduction to Environmental Geology

Environmental Geology is the study of geological processes as they relate to the living environment.
It examines the intersection of geological factors and human activities, highlighting the resulting impacts on the environment, health, and safety.

Module I: Foundations

Planet and Population: An Overview

Lecture Overview

Formation of Our Unique Planet
- Earth’s story is intertwined with the scientific explanation of its formation and age.
Geology as a Science
Population Growth and Its Impact

Human Perspective in the Universe

Quote by Carl Sagan: "We are tiny specks…"
- Humanity exists on a minuscule scale within the vast universe and lives on a planet formed over ~4.5 billion years in a universe that is approximately 14 billion years old.

Big Bang Theory

Definition: The Big Bang Theory is the prevailing cosmological model explaining the origin of the universe.
The universe began as a cosmic explosion approximately between 12 billion and 14 billion years ago, which propelled matter outward in all directions.

Formation of the Galaxy and Solar System

Galaxies
- Initially formed as small clouds of stars and dust in space.
- Through gravitational attraction, these clouds interact and collide, forming larger structures.
Solar System Formation
- The majority of the mass in the cloud coalesced to form the sun, which makes up over 99% of the mass in our solar system.
- Dust remaining in the flattened cloud subsequently formed planets.

Composition and Types of Planets

Composition Dependent on Proximity to the Sun
- Closest planets: Mainly metallic iron, high-temperature minerals, little water, or gases.
- Distal planets: Contain greater quantities of low-temperature minerals, liquid water, and gases.
Planets of Our Solar System:
- Rocky/Terrestrial Planets: Solid rocky surfaces with dense metallic cores.
- Gaseous/Jovian Planets: Large, gaseous bodies comprising small molten rock cores.

The Pluto Debate

In 2006, the International Astronomical Union reclassified Pluto as a Dwarf Planet, not meeting the criteria to be classified as a full planet.

Earth's Formation

Earth formed approximately 4.5 billion years ago.

Earth's Internal Structure

Divided into three layers:
- Crust
- Continental crust consists primarily of granitic rock.
- Oceanic crust mainly composed of basalt.
- Mantle
- Composed of iron-rich silicates and is the thickest zone, encasing the core.
- Core
- Composed of nickel (Ni) and iron (Fe).

Differentiation of Earth's Layers

During cooling, dense materials like iron sank to the center, while low-density minerals crystallized and floated to the surface, leading to the formation of distinct compositional layers.
Crust is chemically distinct from the core or mantle;
- Two types of crust: Oceanic (mafic) and Continental (felsic).

Composition of the Earth

Most Common Chemical Elements in Earth: Analysis based on averages of several estimates reflects the elemental distribution in the Earth.

Formation of Early Atmosphere and Oceans

The heating and differentiation process led to the release of gases and water, ultimately forming the early atmosphere and oceans.
Early Earth atmosphere:
- Significant absence of free oxygen (O2), predominantly nitrogen (N) and carbon dioxide (CO2).
- Included smaller amounts of other gases like methane (CH4), ammonia (NH3), and sulfur gases.
- Climate devoid of life due to lack of oxygen.

Emergence of Early Life

Cyanobacteria

Cyanobacteria, also known as blue-green algae, are believed to be the first life forms to produce oxygen through photosynthesis, utilizing water and CO2 from the oceans.

Signs of Oxygenation

Banded Iron Ore
- Sedimentary rocks indicating the presence of alternating layers of iron oxides and iron-poor chert—suggesting oxygenation of oceans around 2-4 billion years ago.
Stromatolites
- Sedimentary structures formed by photosynthetic organisms like cyanobacteria, peaking in the fossil record about 1.25 billion years ago.

Evolution of Life on Earth

Timeline of Life:
- Little evidence exists for life from 2 billion to 500 million years ago (early life forms contained no hard biological parts).
- Evidence of blue-green algae around 2 billion years ago; multicellular life emerged around 1 billion years ago.
- Marine animals with shells flourished by 600 million years ago.

Human Evolution

Timeline:
- Vertebrates emerged roughly 500 million years ago.
- Land plants introduced about 400 million years ago; insects evolved around 300 million years.
- Dinosaurs thrived about 200 million years ago; birds appeared around 150 million years ago;
- Mammals well established by 100 million years ago; the earliest humans formed 3-4 million years ago, and modern humans (Homo sapiens) emerged in the last 90,000 years.

Geologic Time Scale

Overview of Major Events:
- Demonstrates the progression of significant terrestrial events including mass extinctions, the establishment of ecosystems, and geological transformations.
- Seal these events across eons, eras, periods, and epochs.

The Nature of Geology as a Science

Early geology involved observational techniques; later it transitioned to integrated disciplines like chemistry, physics, biology, and mathematics.
Geology now uses quantitative measurements to establish hypotheses and their validity.
Key aspects of geology include analysis of climate change, mitigation of natural hazards, and controlling erosion and sedimentation.

Scientific Method in Geology

Observations: Collecting empirical data.
Hypothesis formation: Developing testable models.
Testing the hypothesis: Systematic experimentation and prediction.
Data analysis: Results may refine the hypothesis.
Conclusion: After rigorous tests, a hypothesis may evolve into a widely accepted theory.

Challenges in Geology

Size: Large geological structures like volcanoes and tectonic plates aren't easily manipulatable for controlled experiments.
Time: Geologic processes span millions of years, challenging human observational limits.
Resolution of data: Advances in technology reveal more geological details, often challenging existing theories.

Population Dynamics

Population Density (Estimated 2015)

Population density categories (persons per km²) vary significantly across the globe.

Population Growth Trends

Population has experienced notably exponential growth:
- Linear Growth: Same number added each year relative to a starting point.
- Exponential Growth: Growing percentage of population each year relative to the preceding year's total population.
Current population growth is approximately 1%, with historical peak growth rates reported at 2.1% in 1968.

Doubling Time Calculation

Formula for Doubling Time (D):
$D = rac{70}{G}$
where G is the growth rate in %/year.
Global average growth rate is about 1%, resulting in a doubling time of around 70 years.

Future Population Projections

Predicted population of approximately 10 billion by the year 2050 and 11 billion by 2100 based on expected fertility rates.

Challenges Posed by Rising Population

Anticipated issues related to increasing human population:
- Strain on food supply (renewable resources).
- Water scarcity (somewhat renewable).
- Resource limits concerning minerals, fuel, and available land.
- Challenges to sustaining a comfortable living standard amidst increasing population pressures.

Resource Distribution and Water Stress

Resource Inequity: Disparities exist between resource distribution and population concentration.
Water Stress Levels: Various regions demonstrate different stress levels; data visually represented reflect conditions in places like Canada, Russia, and the U.S.

Expected Impact of Declining Fertility Rates

Projections indicate aging populations leading to:
- Rising taxes due to support of aging individuals.
- Potential stagnation in innovation and workforce size.
- Decreases in standard of living as result of limited economic contributions to the workforce.