EAS 210 ALL LECTURES

What are the two main branches of geology?

Physical geology and historical geology.

What does physical geology study?

Earth materials and the processes acting on Earth.

What does historical geology study?

Earth's origin, changes through time, and evolution.

What are Earth's chemical layers?

Inner core, outer core, mantle, and crust.

What is the inner core made of?

Solid iron.

What is the outer core made of?

Liquid iron.

What is the mantle mainly made of?

Silicate minerals containing Fe and Mg.

What is the crust mainly made of?

Silicate minerals containing Na, Ca, and Al.

How do oceanic and continental crust differ?

Oceanic crust is thin; continental crust is thick.

What is the lithosphere?

The rigid outer layer of Earth.

What is the asthenosphere?

A weaker layer beneath the lithosphere.

What evidence did Wegener use for continental drift?

Coastline fit, fossils, ancient mountains, and past glaciations.

What was Pangea?

A supercontinent containing all continents about 300–200 Ma ago.

How is plate motion measured today?

GPS measures plate motion in real time.

How many major tectonic plates are there approximately?

About 16 major tectonic plates.

How fast can a tectonic plate move?

Up to about 20 cm per year.

What happens at plate boundaries?

Relative plate motion produces earthquakes and other geological processes.

What happens at a divergent boundary?

Plates move apart.

What landforms occur at divergent boundaries?

Continental rift valleys and oceanic mid-ocean ridges.

What happens at a convergent boundary?

Plates move toward each other.

Why does oceanic crust subduct?

It is denser than continental crust.

What forms when oceanic and continental plates converge?

A subduction zone and volcanic arc.

What forms when two continental plates collide?

Mountains and large plateaus.

What happens at a transform boundary?

Plates move horizontally past each other.

Why are transform boundaries major earthquake hazards?

Their earthquakes are shallow and involve horizontal ground motion.

What five characteristics define a mineral?

Naturally occurring, solid, crystalline, specific composition, usually inorganic.

What is a mineral's crystalline structure?

A regular internal arrangement of atoms.

What is a gemstone?

A mineral or rock used decoratively as a precious or semi-precious material.

What is atomic number?

The number of protons in an atom's nucleus.

What determines an element's identity?

The number of protons in its nucleus.

What is atomic weight in these notes?

The total number of protons and neutrons in the nucleus.

What are isotopes?

Atoms of an element with different numbers of neutrons.

How do isotopes affect atomic number?

They do not change the atomic number.

Why are some isotopes useful for dating rocks?

Unstable isotopes undergo radioactive decay.

What controls an atom's chemical reactions?

The arrangement of its outermost electrons.

What electron arrangement is especially stable?

A full outer orbital, like noble gases.

What are the four bond types in the notes?

Covalent, ionic, metallic, and van der Waals.

Which bond type is strongest?

Covalent bonding.

How does ionic bonding form?

Electrons transfer, forming oppositely charged ions that attract.

What is a cation?

A positively charged ion.

What is an anion?

A negatively charged ion.

What is an example of an ionic mineral?

Halite (NaCl).

How does covalent bonding form?

Atoms share electrons.

What are polymorphs?

Materials with the same chemical formula but different atomic arrangements.

What is a metallic bond?

A bond involving shared, mobile electrons among atoms.

Where do van der Waals bonds occur in minerals?

Between sheets in mica and graphite.

What are the eight common crustal elements listed?

O, Si, Al, Fe, Ca, Na, K, and Mg.

Which two elements dominate Earth's crust?

Oxygen and silicon.

What are native elements?

Minerals composed of a single element.

Name four native elements from the notes.

Gold, silver, copper, and sulphur.

What are sulphide minerals?

Minerals containing sulfur plus a metallic element.

Name four sulphide minerals from the notes.

Pyrite, sphalerite, chalcopyrite, and galena.

What are oxides?

Minerals containing oxygen combined with metallic elements.

What is special about magnetite?

It is magnetic.

What is hematite an important source of?

Iron ore, especially in banded iron formations.

What is corundum's Mohs hardness?

9, making it the second hardest mineral after diamond.

What are halides?

Minerals whose anion is a halogen such as F, Cl, or I.

Name three halide minerals from the notes.

Halite, sylvite, and fluorite.

What is the silica tetrahedron?

A SiO4 unit with a -4 charge.

How are silicate charges balanced?

Cations such as metals balance the negative charge of silica tetrahedra.

What four silicate structures are listed?

Nesosilicates, inosilicates, phyllosilicates, tectosilicates.

What is a nesosilicate?

A silicate with isolated tetrahedra.

What is an inosilicate?

A silicate with chains of tetrahedra.

What is a phyllosilicate?

A silicate with sheets of tetrahedra.

What is a tectosilicate?

A silicate with a 3-D framework of tetrahedra.

What are ferromagnesian silicates generally like?

Dark coloured and heavy; Fe/Mg are major cations.

What are non-ferromagnesian silicates generally like?

Light coloured; K/Ca/Na are major cations.

What are the three major rock types?

Igneous, sedimentary, and metamorphic.

How do igneous rocks form?

Molten rock solidifies.

What is magma?

Molten rock beneath Earth's surface containing melt, crystals, water, and gas.

What is lava?

Magma after it reaches Earth's surface.

What is a crystal mush?

A partially molten region containing melt and solid mineral grains.

What is an intrusive igneous rock?

Rock that cools slowly underground.

What is an extrusive igneous rock?

Rock that reaches the surface and cools quickly.

How does silica affect magma?

Higher silica generally means higher viscosity and a lower melting point.

What is felsic magma?

High silica, lower melting point, and high viscosity.

What is mafic magma?

Low silica, higher melting point, and low viscosity.

What is the average continental geothermal gradient at the surface?

About 25 °C per km.

What three changes can generate magma?

Add heat, decrease pressure, or add volatiles.

What is phaneritic texture?

Large visible crystals from slow cooling.

What is aphanitic texture?

Small crystals from fast cooling.

What is pyroclastic texture?

A fragmental texture made from volcanic particles travelling through air.

What is glassy texture?

Very rapid cooling prevents crystals from forming.

What causes vesicular texture?

Gas bubbles expand near the surface and cannot escape.

What is porphyritic texture?

Crystals form during different cooling rates, producing mixed grain sizes.

What is granite?

A felsic intrusive igneous rock with large grains.

What is rhyolite?

A felsic extrusive igneous rock.

What is gabbro?

A mafic intrusive igneous rock.

What is basalt?

A mafic extrusive igneous rock.

What is peridotite?

An ultramafic intrusive rock dominated by olivine.

What is obsidian?

A usually felsic extrusive igneous rock with glassy texture.

What is pumice?

A highly vesicular, frothy extrusive rock that can float.

What is scoria?

A frothy extrusive rock analogous to pumice but associated with mafic magma.

What is a dyke?

A tabular, discordant intrusive body.

What is a sill?

A tabular, concordant intrusive body.

What is decompression melting?

Melting caused by lowering pressure as hot mantle rises.

How can subduction generate magma?

Water from the descending slab acts as a volatile and promotes melting.

What controls lava viscosity most directly in these notes?

Silica content.

How does increasing silica affect viscosity?

It increases viscosity.

How does increasing temperature affect viscosity?

It decreases viscosity.