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GEOL105

Exam 2 Study Guide

S23

~50 questions, taken on Canvas. Use your study guide during the exam.

1. Study lecture notes, be able to answer questions

Can you answer the ‘Check Your Understanding’ questions at the end of each section?

2. Take online Quizzes 3, 4 and 5

3. Practice Reading Assignments 5,6,7,11

4. Be prepared to interpret maps and figures to illustrate concepts.  Do you understand the graphs and figures in the assigned chapters?  What about recent news articles featuring volcanoes and flooding?

Chapter 5: Volcanoes

· Magma composition

o Basaltic vs andesitic vs rhyolitic –

§ silica composition

§ temperature

§ viscosity

§ volatiles

§ And how these variables interrelate

o Phase diagrams – pressure vs temperature; role of volatiles

o Three mechanisms of magma generation:

§ decompression melting (primarily divergent boundaries)

§ conduction heating (addition of heat).  Conduction melting occurs to some extent at hotspots and subduction zones.

§ addition of volatiles to lower melting point at subduction zones

o 3 V’s: viscosity, volatiles, volume determine eruption style AND volcano structure

· Volcanic landforms and eruption styles

o Shield

o Cinder cone

o Lava dome

o Stratovolcano

o Continental Caldera

· Volcanic hazards

o Relationship of hazard to magma viscosity and volatile content

o Relationship of hazard to tectonic setting and volcano structure

o Are lava flows dangerous?

o Tephra/Pyroclastics – lava bombs, lapilli, ash fall

o Pyroclastic flows – continental caldera, stratovolcano, lava dome collapse, lateral blast

o Understanding risk based on evidence in the historic and geologic records

Chapter 6: Rivers and Flooding

· Hydrologic cycle

o runoff, precipitation, infiltration, interception, evaporation

· Basic river processes

o What is a stream? Why is it important to define a stream channel?

o Watersheds: definition, importance of this concept

o Zone 1 (erosion): headwaters, Zone 2 (transport):  floodplains, meanders, Zone 3 (dposition): base level

§ within each zone, relative to the others:
elevation? gradient? channel shape? erosion vs deposition?

o Calculate a channel gradient

o Sediment transport -- total load= bed load + sediment load + dissolved load

o Floodplain -- meandering vs braiding

o What is discharge? What is peak discharge? The components of discharge?

§ Be able to calculate a discharge: Q = VA

o Stage (how to measure); bankfull stage vs flood stage

o Hydrograph: plot of discharge (or stage) vs. time

o What is lag time? What factors can increase or decrease lag time?

· Flooding:

o Compare and contrast geographic risk of flooding

§ Flash floods – Zone 1

· characteristics of flash floods, properties specific to Zone 1 regions that specifically precipitate ( flash floods

§ Downstream floods -- Zone 2, Zone 3

· characteristics of downstream floods

· contrast downstream floods with flash floods

· properties specific to Zone 2 that precipitate flash floods

§ Megafloods – Ex: California “Pineapple Express”

o Linkage of flooding with other natural hazards

§ Hurricanes, tsunamis

§ Landslides, earthquakes, even volcanoes (lahars!)

o Benefits of periodic flooding

· Human influence on flood hazard

o Structural influences: Levees, Dams, Urbanization and impervious surfaces

§ Stream restoration, ecological pros and cons

o Analyzing risk:  Flood maps, Recurrence interval

o What is a 10-year flood, a 100-year flood?

Chapter 11: Coastal Hazards

· Relative vs. Eustatic sea level: what causes these to change?

· Wave properties: wave height, wavelength, period

· How waves are formed: roles of wind speed, duration, fetch

· Wave refraction: waves bend to focus on energy on coastal headlands leading to greater erosion. Lower energy waves are associated with gently sloping beaches.

· Tides: what causes tides? How are neap and spring tides different than regular tides?

· Be familiar with the anatomy of a beach.

o Onshore: cliff, dunes, berm, beach face, swash zone

o Offshore: longshore bar and trough occur at breaker zone

o Farther offshore: continental shelf, submarine canyon, abyssal plain

· Understand the difference between tectonically active and passive coasts

Active coasts (Ex: Pacific): near tectonic boundary, erosive environment

o plunging waves

o rocky features like arches, stacks, cliffs

Passive coasts (Ex: Atlantic/Gulf): not near plate boundary, depositional environment

o spilling waves

o sandy beaches

o depositional features governed by longshore drift like spits, baymouth bars,
barrier islands

o depositional seasonal cycle:

§ summer storage of sand onshore
(enriched beach, larger dunes, depleted longshore bar)

§ winter storage of sand offshore
(depleted beach, smaller dunes, enriched longshore bar)

· Understand how the longshore current leads to sediment transport (longshore drift) and contributes to coastal erosion. Be able to determe the direction of the current and anticipate sites of sediment erosion and deposition.

· Recognizer process that add or remove sediment from coasts

o additive – river delta deposition, longshore drift, seacliff erosion

o subtractive – erosion (from longshore drift carrying away), submarine canyon

· Be familiar with engineered structures humans build to control coastal erosion

o Hard structures: jetties, groins, breakwaters, seawalls

o “Soft” structures: beach nourishment, dune stabilization

· Recognize other related hazards: hurricanes, storm surges