PLSS/EVSC 201 Chapter 1: Introduction to Geology

Flashcards reviewing key concepts, Earth systems, mechanical and compositional layers, plate tectonics, heat engines, and geologic time principles from PLSS/EVSC 201 Chapter 1.

What is the origin and literal meaning of the word 'Geology'?

It comes from the Greek words geo (Earth) and logos (discourse), and is defined as the scientific study of the earth.

What is the primary focus of Physical Geology?

It examines Earth's rocks and minerals and seeks to understand processes that operate on the surface and beneath the earth.

What does Historical Geology examine?

It examines the origin of Earth and its development through time.

According to the lecture notes, when did Earth form?

Earth formed $4.6\text{ billion}$ years ago.

What four major environments make up the Earth system?

1. The Hydrosphere
2. The Atmosphere
3. The Biosphere
4. The Geosphere or Solid earth

Which three Earth environments constitute the Physical Environment?

The solid earth, hydrosphere, and atmosphere.

What percentage of Earth's surface is covered by the hydrosphere, and how much of Earth's water is in the ocean?

The hydrosphere covers $71\%$ of Earth's surface, and the oceans contain $97\%$ of Earth's water.

What are the three compositional layers of Earth, defined by changes in chemical composition and density?

1. Crust
2. Mantle
3. Core

What is the thickness range of Earth's crust?

Earth's crust ranges from $5\,km$ ($3\,mi$) to greater than $70\,km$ ($40\,mi$).

What proportion of Earth's total volume does the mantle occupy?

The mantle is the largest portion of Earth by volume, occupying approximately $80\%$.

What is the chemical composition of Earth's core?

The core is made of metal: iron ($\text{Fe}$), nickel ($\text{Ni}$), plus a small amount of a lighter element, probably sulfur ($\text{S}$).

What are the structural dimensions of Earth's outer core and inner core?

The outer core is a molten metallic layer about $2270\,km$ ($1,400\,mi$) thick. The inner core is a solid iron-rich sphere with a radius of $1216\,km$ ($756\,mi$).

What components form the Lithosphere, and what is its thickness?

The Lithosphere is composed of the crust and upper mantle, forming a cool, rigid shell about $100\,km$ thick.

What conditions exist in the upper $150\,km$ of the Asthenosphere?

The temperature and pressure regime allows a small amount of melting ($1\text{--}5\%$) to take place.

Who proposed the Continental Drift hypothesis in the early 20th century?

Alfred Wegener.

What are the three main types of plate boundaries and their relative motions?

1. Divergent: Plates move apart.
2. Convergent: Plates move toward each other.
3. Transform: Plates move sideways past each other.

What process occurs at convergent plate boundaries when two plates meet?

Subduction occurs, where the denser of the two plates sinks beneath the other and is reabsorbed into Earth's interior.

What is Rifting in plate tectonics?

Rifting is the process where pulling action generated by slow-flowing currents in the asthenosphere tears existing plates apart into two or more smaller plates.

What is the average annual rate of plate movement?

Plates move about $1$ to $10\,cm/yr$ ($0.5$ to $4\,ins/yr$).

What drives Earth's internal processes such as volcanoes, earthquakes, and mountain building?

Heat moving from the hot interior to the cooler exterior via convection, and the radioactive decay of elements, principally uranium ($\text{U}$), thorium ($\text{Th}$), and potassium ($\text{K}$).

What process inside Earth generates its magnetic field?

Convection in the metal core.

What is lithification?

Lithification is the process of solidifying weathered sediments into sedimentary rocks through burial.

How does Catastrophism explain Earth's geological history?

It posits that Earth was shaped entirely by sudden, short-lived, violent catastrophic events.

What is the Principle of Uniformitarianism and who proposed it?

Proposed by Hutton, it states that the physical, biological, and chemical laws operating today also operated in the geologic past ('The present is the key to the past').