Geology and Earth Systems Flashcards

Flashcards covering Earth systems, history of geological thought, stratigraphy principles, and the classification/formation of minerals and rocks.

How is geology defined?

Geology is the science of Earth.

What is a system in the context of Earth science?

A series of parts or components that interact to produce a larger, more complex whole, or a part of nature.

What three types can systems be?

Open System, Closed System, and Isolated System.

What are the four major open systems (spheres) of Earth?

Atmosphere, Geosphere, Hydrosphere, and Biosphere.

What is the atmosphere, and what does its Greek root mean?

The gaseous envelope surrounding Earth; its Greek root "atmos" means vapor or smoke.

What is the hydrosphere, and what does its Greek root mean?

All the water on the surface (and within the crust) of the Earth; its Greek root "hydro" means water.

What is the cryosphere?

All the frozen water on the surface of the Earth, sometimes recognized separately from the hydrosphere.

What is the biosphere, and what does its Greek root mean?

All living things on Earth; its Greek root "bio" means life.

What is the anthroposphere?

All the parts of the Earth's environments that are made or modified by humans and used for human activity.

What is the geosphere, and what alternate term is often preferred when referring to integrated Earth systems?

All the physical features of the solid Earth (from the Greek root "ge(o)" meaning Earth); often referred to as the "solid Earth system."

What are cycles in Earth systems?

Organized systems of interactions between major Earth systems, such as the Rock Cycle, Hydrologic Cycle, and Carbon Cycle.

What were the geological contributions of Xenophanes ($\sim 570-475\,\text{BC}$)?

He was the first to recognize fossils, realized fossil shells and fish meant land had once been underwater, and was the first to use fossils as evidence for Earth history.

What did Herodotus ($\sim 484-425\,\text{BC}$) recognize from fossils in Egypt?

He independently recognized that fossils found in Egypt meant some parts of the land had once been an ocean.

Who was Hippocrates ($\sim 460-370\,\text{BC}$) in the context of Earth history?

The first known fossil collector.

What contributions did Theophrastus ($\sim 371-287\,\text{BC}$) make to geology?

Known as the "Father of botany," he wrote "On Stones" (the first extended catalogue and description of minerals and rocks) and created the first known classification of rocks.

What were the major geological achievements of Pliny the Elder (AD $24-79$)?

He wrote "Naturalis Historia" (essentially inventing the encyclopedia), pioneered crystallography, and was the first known to recognize amber as fossil tree sap before dying during the eruption of Mt. Vesuvius at Pompeii.

Who is known as the "father of stratigraphy"?

Nicolas Steno (Niels Steensen, $1638-1686$).

What is Steno's Principle of Original Horizontality?

Most strata (layers of rocks or sediment) are deposited nearly horizontal, parallel to the Earth's surface.

What is Steno's Principle of Original Lateral Continuity?

Layers of sediment initially extend laterally in all directions until the environment changes, they thin out at basin margins, grade into different sediment, or are terminated abruptly by a barrier to sedimentation.

What is Steno's Principle of Superposition?

In an undisturbed sequence of strata, as sediment is deposited it buries previously deposited sediment, making the oldest layers at the bottom and successively younger layers above.

What are geopetal structures used for?

They indicate which way was originally up in strata that have been tilted past vertical and preserved overturned.

What is the Principle of Cross-Cutting Relationships?

A geological feature which cuts another is the younger of the two features.

Who is known as "The Father of Modern Geology"?

James Hutton ($1726-1797$).

What is Uniformitarianism?

The ideology often summarized as "the present is the key to the past," stating that processes operating today also operated in deep time and explain most things in the rock record.

What is a modern caveat to strict Uniformitarianism?

Major processes operated in the past that are not operating in the world at present, such as epicontinental seas.

What is Catastrophism?

The idea that major Earth change was concentrated in periods of sudden, violent change.

What is Neptunism and who proposed it?

Proposed by Abraham Gottlob Werner ($1750-1817$), Neptunism explained geological features as having crystallized from a primordial ocean.

What is Plutonism?

A rival explanation to Neptunism around the turn of the 19th century which recognized that granite, basalt, and other igneous rocks were formed from molten magma.

What major work did Charles Lyell ($1797-1875$) publish, and what was its significance?

He published the three-volume "Principles of Geology" ($1830-1833$), which popularized uniformitarianism, served as the foundation of modern geology, and codified stratigraphy as a science.

What is the Principle of Included Fragments?

Formulated by Lyell, it states that fragments of rock or clasts in a larger rock are older than the rock itself.

Who created the first geological map of Britain, and what principle did he formulate?

William "Strata" Smith ($1769-1839$); he formulated the Principle of Faunal (Biotic) Succession.

What is the Principle of Faunal (Biotic) Succession?

Fossils appear in strata in a definite and determinable order.

What is the geological definition of a rock?

A naturally formed, consolidated mixture of minerals.

What is the geological definition of a mineral?

A naturally occurring crystalline solid with a definite chemical formula.

Can purely monomineralic rocks occur in nature?

No, purely monomineralic rocks do not occur naturally, though in petrology rocks are termed monomineralic when a single mineral is dominant ($> 0.90$ of one type).

What five criteria define a mineral?

A mineral must be inorganic, occur in nature, be solid, have a definite and fixed composition, and have a distinct crystalline structure.

What is a crystalline structure?

An arrangement where atoms are organized in a regularly repeating 3-dimensional pattern called a crystal lattice.

What four ways can minerals form?

Crystallizing from molten material, precipitating from fluids, weathering reactions and sedimentation, and metamorphic processes.

What is streak in mineral identification?

The color left behind when a mineral is scraped on unglazed porcelain.

What is luster in mineral identification?

The manner in which light reflects off the surface of a mineral, classified into metallic and non-metallic luster.

What is the difference between cleavage and fracture in minerals?

Cleavage is breakage along flat planes, while fracture is irregular breakage.

What is specific gravity?

The density of a mineral relative to that of water.

How does calcite react to chemical testing?

Calcite fizzes in dilute $\text{HCl}$ (hydrochloric acid).

How do igneous rocks form and how are they classified?

They form from solidifying magma or lava as it cools; classification is based mostly on mineral composition (felsic vs. mafic/ultramafic) and mode of origin (intrusive vs. extrusive).

What are intrusive and extrusive igneous rocks?

Intrusive (plutonic) rocks form from magma cooling inside the Earth; extrusive (volcanic) rocks form from lava on the Earth's surface.

What are examples of igneous rocks formed from pyroclastic flows?

Tuff, volcanic breccia, obsidian (volcanic glass), pumice, and scoria.

How are metamorphic rocks formed and what is foliation?

They are formed by alteration of pre-existing rock under heat and pressure; foliation is the alignment of crystal growth in response to stress.

What is the sequence of foliated metamorphic rocks from low to high grade?

Slate $\rightarrow$ Phyllite $\rightarrow$ Schist $\rightarrow$ Gneiss.

What are two examples of non-foliated metamorphic rocks?

Marble and quartzite.

What are the four forms of metamorphism described in the notes?

Regional metamorphism, contact metamorphism, burial metamorphism, and hydrothermal metamorphism.

How are clastic sedimentary rocks classified by grain size and texture?

By grain size (Gravel $> 2\,mm$, Sand $2-0.0625\,mm$, Mud $< 0.0625\,mm$), sorting (time in transport), and rounding (time in transport).

What distinguishes conglomerate from breccia?

Both are gravel-sized clastic sedimentary rocks ($> 2\,mm$), but conglomerate has rounded clasts while breccia has angular clasts.

What distinguishes shale from claystone?

Shale is laminated clay ($< 0.0039\,mm$), whereas claystone is nonlaminated clay.

How do chemical evaporite sedimentary rocks form and what are three examples?

They form when water evaporates in arid terrestrial regions, restricted coastal plains, or marine basins with restricted circulation; examples include halite, gypsum, and anhydrite.

What is chert?

A chemical sedimentary rock formed when microcrystalline quartz is precipitated from silica-rich water.

What is chalk?

A biogenic carbonate limestone made almost exclusively from the plates secreted by microscopic algae called coccolithophores.

What are ooids and how does oolite form?

Ooids are small, spherical or ellipsoidal grains composed of concentric mineral layers around a nucleus; oolite forms in very shallow, warm, and agitated marine environments.

How does coal form and in what environment?

Coal forms by the accumulation and compaction of plant material in anoxic swamp or peat bog environments.

Why are sedimentary rocks especially critical for Earth history?

They contain fossils.