GEOL 105 - Exam 2 (Dr. Rezene Mahatsente)

Rock that was once a melt / magma

(Lecture 7)

What are Igneous Rocks?

Magma: Melt at depth. Solidified = intrusive/plutonic rock

Lava: Magma at surface. Solidified = extrusive/volcanic rock

(Lecture 7)

Difference between Magma and Lava

Based on the percentage of silica

(Lecture 7)

How to tell the type of composition of Magma?

Felsic, Intermediate, ultramafic, and mafic

(Lecture 7)

Different types of Magma composition

1. Silica Rich

2. Made of feldspar and quartz

3. Non-ferrromagnesian silicates

4. Continental crust is Felse

(Lecture 7)

Felsic - Magma

1. 53-65% Silica

2. Contains more than 25% ferromagneisan minerals

(Lecture 7)

Intermediate - Magma

1. Silica poor = 45-52%

2. Ferromagneisan silicates & ca-rich feldspar

3. Oceanic crust & volcanic islands are mafic

(Lecture 7)

Mafic - Magma

1. <45% silica

2. Rare

3. Entirely ferromagnesian silicates

(Lecture 7)

Ultramafic - Magma

1. High Silica = High viscosity = Low mobility

2. Low Silica = Low viscosity = High mobility

(Lecture 7)

Explain the relation between the silica content of a magma and viscosity

1. Mafic: HIgh mobility due to low silica

2. Intermediate: Low mobility due to high silica

(Lecture 7)

Mobility of types of Magma

1. Magma rises up into the crust

2. Temperature increases in the upper crust due to magma

3. Crustal rocks near melting points

4. More heat will melt some upper crust

(Lecture 7)

Magma Formation - Hypotheses 1: Heat Transfer

1. More pressure will increase rock's melting temperature

2. When pressure drop, decompression melting starts

(Lecture 7)

Magma Formation - Hypotheses 2: Decompression Melting

1. Break chemical bonds (hot rock + water = melt)

2. Cause rocks to melt at lower temperature

3. Happens in Subduction Zone

(Lecture 7)

Magma Formation - Hypotheses 3: Volatiles or Flux Melting

1. Composition of magma changes during crystallization

2. It crystallizes in predictable sequence

3. All magmas come from mafic magma

(Lecture 7)

Bowen's reaction Series

1. Continous = Calcium rich Plagioclase feldspar

2. Disconintous= Olivine, Pyroxene, Amphibole, Biotite mica

(Lecture 7)

Bowen's Continuous and discontinuous reaction series.

1. Potassium feldspar

2. Muscovite mica

3. Quartz

(Lecture 7)

What is the end result of Bowen's reaction series

Refers to the temperature variation in the Earth.

(Lecture ?)

Geotherm

Deep-seated intrusion of igneous rock

(Lecture 7)

Pluton

1. Largest pluton

2. >100+km²

(Lecture 7)

Pluton: Batholith

1. Lens or mushroom-shaped pluton

2. Arches overlying strata upward

(Lecture 7)

Pluton: Laccolith

Tabular, concordant pluton

(Lecture 7)

Pluton: Sill

Tabular, discordant pluton

(Lecture 7)

Pluton: Dike

Products of mechanical & chemical weathering

(Lecture 8)

Sediment Rock

Lithification: Compaction by pressure, cementation

Diagensis: Chemical, physical, & biological changes after sediment arrives

(Lecture 8)

Sediment Rocks: Lithhification vs. Diagenesis

1. Grains are squeezed together

2. Reduction in porosity

3. Cementation

(Lecture 8)

Effects of Diagenesis

1. Composed of Calcite

2. Organic Limestone: From reef, shells, & chalk

3. Inorganic limestone: Precipitation from water

(Lecture 8)

Sediments: Chemical Rock - Limestone

1. Formed from limestone

2. Calcite replaced with dolomite mineral

(Lecture 8)

Sediments: Chemical Rock - Dolostone

1. Evaporation triggers depostion of precipitates

2. Formed by gra

(Lecture 8)

Sediments: Chemical Rock - Evaporite

1. Organic origin

2. Biochemical

3. Plant Material → Peat → Lignite → Bituminous

(Lecture 8)

Sediments: Chemical Rock - Coal

(Lecture 8)

Sediment once in solution / by composition

(Lecture 8)

Chemical Rock Identification

By composition

(Lecture 8)

Biochemical Rock Identification

Metamorphism: Physical & chemical changes to rocks due to temperature/ pressure increase

Diagensis: Physical, chemical, & biological changes to rocks due to sediment settling

(Lecture 8 & 9)

Difference between Metamorphism (8) and Diagensis (9)

1. Occurs in Subduction zone

2. High temperature

3. Low presssure

Lecture 9

Blueschist

1. Original Rock before Metamorphism

2. Igneous, Sedimentary, or old metamorphic rocks can be protolith (test question)

Lecture 9

Protolith

1. A Metamorhpic environment

2. Intruding Magma increases temperature (Magma from chamber rising to crust)

3. Heat + Rock = Metamorphism

4. Produces zone of alteration

Lecture 9

Metamorphic Auerole

1. Minerals crystallize and grow butt

2. Minimal defomration and the absecne of compression and shear make non-foliated

Lecture 9

What is a non-foliated metamorphic rock?

1. Hornfels (fine grain)

2. Marble (coarse)

3. Quartzite (large grains, interlocking)

Lecture 9

Examples of Non-foliated metamorphic

1. Temperature increase from intruding magma

2. Produces zone of alteration (mm auerole)

3. Contact metamorphism in rock surrounding magma

(Lecture 9)

Types of Metamorphic environmets - Contact or Thermal

1. Associated with mountain buliding process (orogeny)

2. Affects large area of tectonic activites (regional)

3. Rocks once near the surface ends up at great depth

4. Agents of MM: Heat, Pressure, Compression/shearing

(Lecture 9)

Types of Metamorphic environment - Regional or dynamothermal

It should have nothing on study guide

Lecture 10

1. Shield volcanoe

2. Cinder Cones

3. Stratovolcanoes/ composite volcanoe

(Lecture 11)

The different forms of subaerial volcanoes

1. Broad and gentle dome

2. Born from low viscosity basaltic lava flows

(Lecture 11)

Subaerial Volcanoes - Shield

1. Cone-shaped, deep craters in summit

2. Form from piles of tephra

(Lecture 11)

Subaerial Volcanoes - Cinder Cones

1. Cone-shaped, large, steep, crater at summit

2. Form from layers of lava, tephra, and debris

(Lecture 11)

Subaerial Volcanoes - Stratovolcanoes/ composite volcanoes

1. Ejecta volume >1,000 km³

2. Example: Yellowstone

(Lecture 11)

Supervolcano

1. Pahoehoe lava

2. Aa Aa lava

3. Others not on study guide

(Lecture 11)

Volcanic Materials: Extrusive Materials

Warm pasty surface

(Lecture 11)

Volcanic Materials: Extrusive Materials - Pahohoe lava

Rough, blocky

(Lecture 11)

Volcanic Materials: Extrusive Materials - Aa Aa lava

1. Ash <2mm

2. Lapilli 2-64 mm

3. Bomb >64 mm

(Lecture 11)

Volcanic Materials: Extruded Material

Forms when basaltic lava rapidly chilled under water

(Lecture 11)

Pillow Lava

Basaltic: Hot, low silica, gentle lava

Rhyolitic: Silica-rich, viscous, explosive

(Lecture 11)

Basaltic & rhyolitic lava

Should be nothing

(Lecture 12)

1. Ice

2. Glaciers hold the most amount of sediment

(Lecture 13)

Which medium carries the largest particles?

The driving forces and resisting forces determines materials movement on hillslop

(Lecture 13)

Force Balance

Driving Force: Force per unit area

(Lecture 13)

Shear Stress

Resisting Force

(Lecture 13)

Shear Strength

1. Lowers rock strength

2. Two Types - Chemical and Physical

(Lecture 13)

Weathering

1. Chemical: Common in humid-tropical regions

2. Physcial:

(Lecture 13)

Chemical and Physical Weathering

1. River processes or processes associated with stream channels

2. Includes erosion and transporation

(Lecture 14)

Fluvial Process

1. Scouring

2. Breaking and lifting

3. Abrassion

4. Dissolution

(Lecture 14)

The Types of Erosion

Removal of lose fragments of channel walls by running water

(Lecture 14)

Erosion - Scouring

Running water can break solid rocks and lift off the substrate

(Lecture 14)

Erosion - Breaking and lifting

Grinding of channel floor and walls by sediment laden water - can act like sandpaper

(Lecture 14)

Erosion - Abrassion

Running water dissolves soluble minerals

(Lecture 14)

Erosion - Dissolution

1. Dissolved load

2. Suspended stream's load

3. Via saltation

(Lecture 14)

Sediment Transport Types

Bed Load: Grains knocked by the stream follow curved trajectory - sink to the bed - knock another grain

(Lecture 14)

Sediment Transport - Saltation