ERTH 1006 - Midterm

geocentric model

A view of the universe developed by Aristotle and Ptolemy, stating that the Earth is the center of the solar system and the universe.

heliocentric model

The correct model of the solar system, developed by Copernicus, stating that the Sun is at the center of the solar system and the planets revolve around it.

Galileo’s contribution to astronomy

The development of the modern telescope.

Newton’s contribution to astronomy

The laws of planetary motion.

Einstein’s contribution to astronomy

The development of the theories of general and special relativity

Hubble’s contributions to astronomy

The discovery of the first galaxies, and that all galaxies are moving away from each other (red shift).

The Big Bang Theory

The universe began from an infinitely small and dense point that began expanding outwards, creating all matter in and light in the process.

stellar nucleosynthesis

The fusion of elements in the core of stars, producing all elements up to Iron (#56).

supernova

The explosive death of a star, sufficient temperature is reached to form elements heavier than iron, which are scattered as dust into gas clouds.

nebula

A cloud of gas and dust in space that can form a star.

giga annum (Ga)

1 billion years

mega annum (Ma)

1 million years

the nebular theory

Nebulas contract and rotate under gravity, compressing and heating central material until nuclear fusion begins forming a star, lighter material is flung far away while heavier material accretes into terrestrial planets.

refractory material

Dense, heavy material that forms terrestrial planets.

volatile material

Light, less dense material that forms Jovian planets (gas and ice giants).

chondritic meteorite

Meteorites with the composition of refractory material, the building blocks of planet Earth.

stony (achondritic) meteorites

Meteorites with the same composition as Earth rocks.

iron meteorites

Very dense meteorites made from iron and nickel.

causes for early Earth’s extreme heat

Bombardment from meteorites/planetesimals, compression heating, and decay of radioactive elements.

differentiation of the Earth

During Earth’s liquid stage, denser elements sunk to the center of the planet and lighter ones floated to the surface.

chemical layers of the Earth

Core, mantle, crust.

mechanical layers of the Earth

Inner core, outer core, lower mantle, upper mantle, crust.

chemical composition of the crust

Light silicate minerals

chemical composition of the mantle

Heavy silicate minerals

chemical composition of the core

Iron, nickel

matter state of the inner core

Solid

matter state of the outer core

Liquid

matter state of the lower mantle

Rigid solid

matter state of the upper mantle

Ductile solid

matter state of the crust

Rigid solid

highlands

Light-coloured and cratered lunar features made of anorthosite (feldspar)

maria

Dark-coloured lava flows filling in impact basins, mafic rock

regolith

Debris on the moon from meteorite impacts

relative dating

Determining the age of rocks relative to other rocks/features near it.

numeric dating

Determining the actual age, in years, of a specimen.

geochronology

Determining the numeric age of rocks using radiometric dating.

parent and daughter isotopes

An unstable isotope and the element that it decays into.

half-life

The time it takes for half of the parent material to decay into daughter material.

assumptions in radiometric dating

Closed system (no addition/loss of parent or daughter), radiometric “clock” starts upon crystallization, decay rate is constant and accurate.

age of the Earth

4.56 billion years

characteristics of oceanic crust

Mafic rock, lower silica content, thinner crust, denser rock.

characteristics of continental crust

Felsic rock, higher silica content, thicker crust, less dense

orogen

A large mountain range formed by the collision of tectonic plates.

formation of orogens

Thin, dense oceanic crust subducts under continental crust, once the oceanic crust is subducted, the continental crusts collide and crumple to form mountains.

Earth’s first atmosphere

Mostly hydrogen and helium, swept away by solar wind.

mineral

a naturally occurring, inorganic, crystalline solid with a chemical composition within a set range and an ordered internal structure.

rock

An aggregate of minerals

9 main mineral groups

Silicate, oxide, sulfide, sulfate, halide, carbonate, hydroxide, phosphate, native elements.

polymorphs

Substances with the same chemical formula but different bonding arrangements.

lustre

The way a mineral surface scatters light. Can be metallic or non-metallic (silky, glassy, satiny, pearly, earthy).

hardness

The scratching resistance of a mineral, deriving from the strength of atomic bonds

cleavage

The tendency of a mineral to break along planes of weak atomic bonds, described by the number of planes and their angles.

fracture

The breakage of a mineral that is not along a plane, can be conchoidal or irregular.

streak

The colour of the powder of a mineral, only diagnostic for metallic minerals.

habit

The shape of a mineral’s crystals, often difficult to observe.

the character of a rock is defined by

Its texture and mineralogy.

formation of igneous rocks

Crystallization (cooling) from a melt

key texture of igneous rocks

Interlocking crystals

intrusive/plutonic igneous rocks

Rocks that have formed from magma that cooled slowly within the Earth, allowing for the growth of large crystals.

extrusive/volcanic igneous rocks

Rocks that have formed from magma that cooled quickly at the Earth’s surface, with very small crystals.

formation of sedimentary rocks

The breaking down of other rocks at the surface of the Earth through weathering.

formation of sedimentary rocks

cementation and compaction

pyroclastic rock

Extrusive igneous rock formed from pieces of volcanic debris.

composition of magma

Liquid elements, dissolved gases, solid minerals carried by liquid.

causes of melt

Changes in pressure, temperature, composition.

decompression melting

Process in which melting occurs due to a decrease in pressure on a solid rock. This happens when the rock rises to shallower depths in the Earth's mantle or during tectonic plate movement. It leads to the formation of magma and is responsible for volcanic activity.

hotspot plume

A solid batch of magma rising up through the mantle due to higher temperature, undergoes decompression melting which affects the crust above (volcanoes and intrusions).

partial melting

Process where only a portion of a rock melts, forming magma with a different composition than the original rock, higher in silica.

fractional crystallization

As magma crystallizes, Fe and Mg rich minerals form first, causing the magma to become more silica-rich.

magma mixing

Two different magmas combine to produce a melt of a new composition.

assimilation

Blocks of surrounding foreign rock (xenoliths) are melted into magma, changing composition.

dike

An igneous intrusion that cuts across preexisting rock.

sill

An igneous intrusion that lies parallel to to layering in the host rock.

pluton

A crystallized magma chamber, often irregular in shape.

batholith

A massive intrusive igneous formation that is an entire structure of magma chambers.

weathering

The breaking down of rocks at the Earth’s surface through physical and chemical processes.

erosion

The removal of weathered material from its original rock.

lithification

The process of compaction and cementation that turns sediment into sedimentary rock.

common sedimentary cements

Calcite (CaCO3), quartz (SiO2), hematite (Fe2O3)

clastic sedimentary rocks

Rocks made of fragments of other rocks and minerals (clasts), formed by the process of weathering, erosion, transportation, deposition, and lithification.

chemical rocks

Rocks formed from the precipitation of minerals dissolved in solution.

evaporites

Minerals concentrated by the evaporation of mineral-rich solution.

biochemical sedimentary rock

Rocks composed of shells and shell debris.

bedding

Flat, horizontal layers of sediment that are lithified over time.

laminations

Sedimentary beds less than 1 cm thick.

ripples

Patterns on the surface of sedimentary rocks from previous water flow over sediment.

cross bedding

Cross sections of layers in sedimentary rock that have built on an angle due to dune movement.

graded bedding

The organization of sediment by size within a bed, often due to sediment sliding down an incline.

bioturbation

Disturbances in beds due to plant or animal activity.

body fossils

The preserved form of the bodies of prehistoric organisms.

trace fossils

The preserved form of traces left by prehistoric organisms (footprints, burrows, etc.)

stratigraphic formation

A group of similar sedimentary rocks in the same geographic area.

physical weathering

The breakdown of a rock caused by physical processes that do not alter its chemical composition.

agents of physical weathering

Wind, rain, ice, abrasion

chemical weathering

The breakdown of rock caused by chemical reactions.

agents of chemical weathering

Hydrolysis, oxidation, dissolution

frost wedging

The repetitive freezing and thawing of water within rocks that causes them to weather and break apart.

agents of metamorphism

Changes in pressure, temperature, and composition.

foliation

A planar arrangement of minerals in metamorphic rock.

recrystallization

Changes in the size and/or shape of grains in a rock without changing the composition.