GEO1110 - Exam 1

Physical Geology

Examines the materials composing Earth and processes operating beneath and on Earth's surface.

Historical Geology

Attempts to understand Earth’s origin and its development through time, establishing a chronological arrangement of changes in Earth’s geologic past.

Catastrophism

The theory suggesting that landscapes are shaped primarily by disasters, proposed by James Ussher in the mid-1600s.

Uniformitarianism

Developed by James Hutton in 1795, stating that laws of nature today have always applied, introducing the idea that "the present is the key to the past."

Hypothesis

A tentative, testable explanation in scientific inquiry.

Theory

A well-tested explanation accepted by the scientific community.

Scientific Method

The systematic process for research involving questions, data gathering, and hypothesis testing.

Earth as a System

Consists of interacting parts forming a complex whole: atmosphere, hydrosphere, biosphere, and geosphere.

Divergent Boundaries

plates move apart, creating new seafloor.

Convergent Boundaries

plates move toward each other, forming mountain belts or recycling oceanic lithosphere.

Transform Boundaries

plates grind past one another without lithosphere production or destruction.

Mineral

A naturally occurring, solid, crystalline, inorganic substance with a specific chemical composition.

Rock

A solid mass of minerals or mineral-like matter occurring naturally.

Igneous Rocks

Formed from the cooling and solidification of magma.

Felsic Rocks

Light-colored igneous rocks with high silica content (e.g., granite).

Mafic Rocks

Dark-colored igneous rocks with lower silica content (e.g., basalt).

Rock Cycle

Explains geological processes that form each rock type from the others.

Magma

Molten rock located at depth.

Lava

Molten material that has surfaced.

Silica Content and Magma Behavior

High silica content results in more viscous magma which erupts at lower temperatures, while low silica content leads to less viscous magma which erupts at higher temperatures.

Atmosphere

gaseous envelope

Hydrosphere

global ocean and fresh water

biosphere

all plant and animal life

Geosphere

the solid earth

Inner planets

Mercury, venus, earth, and mars - form from metallic and rocky substances, small and rocky terrestrial planets, “Earth like”

Outer Planets

Jupiter, Saturn, Uranus, Neptune - forming from fragments of ices and gases (H2O, CO2, and others)

Earth’s Internal Structure

Crust

Earth’s thin, rocky outer skin, divided into the continental and oceanic crust. Oceanic curst is 7km thick and composed of basalt. Continental crust is 35-70km thick and composed primarily of granodiorite.

Mantle

2900km thick and composed of peridotite

Core

iron rich

Lithosphere

(rock sphere) the rigid outer layer of the earth that consists of the crust and the upper mantle

Asthenosphere

(weak sphere) the soft, weak layer below the lithosphere

Transition zone

a zone marked by a sharp increase in density below the asthenosphere

Lower mantle

a zone of strong, very hot rocks subjected to gradual flow

outer core

liquid outer layer of core

inner core

solid inner layer of core

Who first proposed the continental drift hypothesis and when?

Alfred Wegener in 1915

Continental drift hypothesis

Super continent named Pangaea, consisting of all of the Earth’s landmasses, once existed.

Around 200 million years ago, this supercontinent began fragmenting.

“drifted” to their present positions over millions of years.

How old is the earth

4.6 billion years old

Whats the radius of the earth?

6371 km

What is the length of the equator of the earth?

6378 km

Evidence for Pangaea

Oceanic ridge system, no oceanic crust is older than 180 million years old, thin sediment accumulation in the deep oceans

Lithosphere (100-200km)

comprised of the crust and upper mantle

asthenosphere (100-200km)

hotter, weaker region of the mantle under the lithsphere

rigid lithosphere overlies weak asthenosphere

Lithosphere and asthenosphere move independently with each other

Evidence of seafloor spreading

used fossil remains of microorganisms for dating, showed that the sediments increased with increasing distance from the ridge.

Major differences between rocks and minerals

A rock is a solid material composed of one or more minerals.
Rocks do not have a specific chemical composition and can be made up of different minerals in varying proportions.

What are the three general processes that form minerals?

1. Precipitation: occurs when a solid forms then falls out of solution

2. Crystallization: similar to water freezing

3. Deposition: as a result of biological processes. Water dwelling organisms transform dissolved material into mineral matter.

Eight most abundant elements in the continental crust

5 rock-forming minerals

Silicate - account fro >90% of Earth’s crust, silicone and oxygen make up the basic building blocks of silicate minerals

Nonsilicate minerals are not as common as silicates but important to our economy.

Carbonates

Oxides

Sulfates

Halides

Rocks are divided into these three major groups

Igneous, sedimentary, metamorphic

Igneous rocks

formed from cooling and solidification of molten rock

sedimentary rocks

• sediments are derived from weathering of preexisting rocks

• undergo lithification which means conversion into rock. Compacted and cemented together

• accumulate in layers at earth’s surface

metamorphic rocks

• formed by changing preexisting igenous, sedimentary, or other metamorphic rocks

• driving forces are heat and pressure

Magma

completely or partly molten rock located at depth

Lava

molten material at the surface

Igneous rocks:

created when magma or lava solidifies

Intrusive igneous rock

magma crystallizes at depth. plutonic rock. example: granite

coarsely grained texture

Igneous compositions - four broad groups based on compositional differences

Felsic, intermediate, mafic, ultramafic

Felsic or granitic composition

• felsic - feldspar and silica

• light colored silicates

• composed almost entirely of quartz and potassium feldspar

• high silica content

• contains small portion of dark silicate minerals

• mamor constituent of continental crust

• example rocks: granite and rhyolite

Intermediate or andesitic composition

• composition between felsic and mafic

• associated with volcanic activity on the seaward margins of the continents and volcanic island arcs.

• Example rocks: diorite, andesite

Mafic or basaltic composition

• mafic - magnesium and ferrum (iron)

• contains dark silicates

• higher density and darker color than granitic rocks

• comprise the ocean floor and many volcanic islands

• forms extensive lava flows on the continents

• example: gabbro and basalt

Crustal rocks exhibit a considerable range of silica content

common silicate minerals in igneous rocks

quartz, potassium feldspar, mica, amphibole, pyroxene, olivine

silica content influences magma behavior

• granitic magmas have high silica content, are viscous (thick) and erupt at a lower temperature

• basaltic magmas have much lower silica content, more fluid like behavior, and erupt at a high temperature