final exam

Question 1

why are some substances, such as radon gas, cobalt or selenium, potentially hazardous?

Answer 1

certain elements, molecules and minerals (i.e. arsenic), weather they are dissolved in water or not, are a medical hazard because they cause illness in living things. for example: mercury causes mental illness
these potentially hazardous substances are usually released from a rock formation as a result of a natural process (i.e radioactive decay) or as the rock/ mineral weathers.

Question 2

what controls the distribution of substances in the environment?

Answer 2

1. the geological source - the rock it came from
2. climate - controls weathering
3. biology - this controls weathering and distribution of these substances after they are released

Question 3

what major problem with determining the health risk of substances?

Answer 3

a major problem when determining the health risk of a substance and what are the effects, effects can be short and long term

Question 4

what is meant by background level when it comes to medical geological hazards such as mercury or lead?

Answer 4

the background level of a potentially harmful substance refers to the concentration that occurs naturally

Question 5

explain the medical hazards associated with radon gas

Answer 5

a naturally occurring radioactive gas emitted by some rocks mainly metamorphic. the hazard is that in high enough concentrations it can cause health problems such as cancer.

Question 6

why is arsenic so hazardous to human health?

Answer 6

Arsenic is nasty stuff. it affects many parts of the human body as it is a poison.

Question 7

in what kinds of deposits is arsenic found in the natural environment?

Answer 7

Arsenic is found in arsenopyrite an iron sulphide mineral that precipitates under (no oxygen) conditions.
Arsenic in arsenopyrite is common in black shales. this is a fine grained layered clastic sedimentary rock that formed in deep, still water, often in the ocean.

Question 8

explain the arsenic hazard in Bangladesh

Answer 8

Himalaya Mts and large river Ganges
the presence of black shales in the. Himalaya Mt is a source for arsenic. the climate in the area promotes weathering. the large rivers between the mountains and the coast transport arsenic south the population centres.
as the result there is high, unhealthy concentration of arsenic in the local groundwater. groundwater is a major source of drinking water

Question 9

why are volcanoes so unstable?

Answer 9

during and between eruptions there is heat and gas . there is also liquid water. therefore inside a volcano there are many different chemical reactions that will weather the volcano. this big pile of loose, weak rock is unstable. volcanoes are prone to failure, they fall down.
what happened when u add water?
1.pore water pressure increases
2.the contact between rocks is lubricated thereby reducing friction
3.weight is added to the structure.
all of these things will increase the possibility that rock will fall off the slides of the volcano: if more rock is removed then the likelihood of an eruption increases because there is less rock to contain the pressure

Question 10

what. is the link between volcanic eruptions and sea water temperature?

Answer 10

1. volcanoes erupt when the rock surrounding the magma chamber cannot contain the pressure
2. the rock that makes up the volcano is weak and unstable
3. what makes this rock even more prone to failure is more water
4. extra water on a volcano comes from the atmosphere in the form of rain or snow
5. most water that eventually falls as rain and snow comes from evaporation of surface water in the oceans
6. warmer sea water increases the rate of evaporation which increases precipitation. it appears then that warmer sea surface temp would conclude with more volcanic eruptions, however, the link is not direct and processes (ocean circulation and volcanic eruptions) are so complex and so different that any link is tenuous at best.

Question 11

what is isostasy

Answer 11

the way the earths crust responds to addition or removal of mass from the surface of the Earth. when mass is added, the crust is pushed down. when mass is removed the crust bounces back up.

Question 12

what is glacial isostatic adjustment?

Answer 12

this is the way the Earths crust responds to the weight of a glacier

Question 13

what is the link between ice ages, the weight of ice and liquid water and earthquakes? give an example.

Answer 13

the effects of glacial ice on earthquakes:
the added weight of an ice sheet on the Earth’s crust will reduce earthquake activity. ice will contain the rock and the stress in it such that the rock can’t move. the effects of liquid water on earthquakes:
the presence of a large body of water on the crust, such as a lake, also represents a significant weight. however, earthquake activity is not inhibited it may even increase beneath a lake.
the weight of all this water forces it into the underlying bedrock where it can cause rocks to move and earthquakes to happen because of increased water pressure in the pores. an example: New Madrid Earthquakes of 1811 and 1812

Question 14

what are the two types of volcano?

Answer 14

Explosive - (Mt. St Helen) type of plate: continental, type of rock: Felsic, lave viscosity: high ( doesn’t flow easily) high silicon content, high amount of trapped gas, rare to erupt, short eruption duration
Effusive - Oceanic plate, Mafic rock, low lave viscosity, low silicon content, low amount of trapped gas, common to erupt, long eruption duration

Question 15

what controls the explosive nature of a volcano?

Answer 15

the explosive nature of a volcano is controlled by the amount of silicon in the silicate minerals in the rocks. the higher silicon content in felsic minerals scubas quarts produces a high viscosity lave when they melt. the thick, viscous lava traps a lot of gas there by creating high potentially explosive pressures.

Question 16

why are volcanoes so hazardous?

Answer 16

1. their explosive force
2. the harmful gasses they release
3. the tsunamis they can create either during or between eruptions
4. the landslides, flows or falls they can cause during and between eruptions

Question 17

during the 1980 eruption of Mt St Helens, in Washington states, geologists were, at first, not convinced the eruption was genuine? why not? as time went by, they became convinced the eruption was genuine and that a major catastrophic event was imminent. what evidence was there to support this conclusion?

Answer 17

Cascade volcanoes like St Helen, often emit gases, especially in late winter and early spring when the snow on them begins to melt, harmonic tremors, small earthquakes around magma chamber also occur. in 1980 None of these caused any alarm, yet as time passed and more attention was paid to this volcano there were more and more signs that a major eruption was likely. what eventually convinced authorities that an eruption could be expected was ash on the snow around the vent on top of the volcano. This confirmed a direct link between the surface and the magma chamber and that pressures inside the volcano had reached dangerous measures

Question 18

what is a flood basalt and why is it so hazardous?

Answer 18

Flood basalts are large, effusive outpouring of lava that covered a very large area of the earth’s surface. these eruptions can last thousand of years. while this outpouring lava is catastrophic for the immediate area there is a much greater hazard. the sustained release of volcanic gases, in particular CO2 can change the atmosphere & oceans. Increased CO2 in the atmosphere will raise air temperature and the lower the pH (acidity) of ocean water. the formation of the Siberian Trops, huge flood basalt deposits at the end of the permian period is thought to be the cause of the largest mass extinction on Earth.

Question 19

discuss the problem associated with an actual or impending eruption of Mt. Vesuvius, Italy and the need to protect the civilian population who live in the area?

Answer 19

a Strato volcano with a long, recorded history of very violent eruptions. Naples is a large, old city surrounding much of this volcano. exposure is high, sensitivity is mixed, so vulnerability is higher that it should. what makes Naples worse, like it does other older European cities, is the infrastructure. Old, less stable buildings, lack of street narrow streets and a lot of people crowded into a small area make evacuation before a catastrophe and response during one more difficult.

Question 20

what is a “tuya volcano” and how is it formed?

Answer 20

a volcano in a mountainous area that is partially or completely enclosed by glacial ice. these volcanoes may form beneath the ice after the glacier has formed. they may also have formed before glaciation and have since been covered in ice.

Question 21

what kind of hazard is associated with a tuya volcano?

Answer 21

the hazard associated with a tuya volcano is not only the force of the eruption but also the large flood of water that may result if the glacier melts. this may result in Lahar, a mud flow associated with a volcanic eruption.

Question 22

what is a tsunami?

Answer 22

a large wave caused by a seismic activity

Question 23

where is a tsunami not a hazard?

Answer 23

in the open ocean, where this low long, fast wave is generated it is not a hazard

Question 24

where is a tsunami most hazardous?

Answer 24

these waves are a significant hazard when they approach a coast. at a coastline, as water depth decreases the energy of this wave and the water is displaced. this forces the wave upward, as length decreases the height increases

Question 25

how are tsunamis generated?

Answer 25

when energy is transformed from crust to the water - a seismic event

Question 26

how does an earthquake generate a tsunami?

Answer 26

during an earthquake the crust beneath the ocean must move vertically. as the surface of the ocean returns to normal, the hole fills in. a series of waves are generated that travel outward from this point of origin

Question 27

how does a volcano generate a tsunami?

Answer 27

1. an explosive eruption next to or beneath the ocean can generate a tsunami
2. the collapse of an underwater volcanoes as the magma chamber empties during an eruption
3. underwater landslides from a volcano between eruption

Question 28

what particular features of a shield volcano contribute to the creation of a tsunami?

Answer 28

as a shield volcano forms it does so on the sea floor. because lava cools very quickly on contact with water. the rock that forms has little or no crystalline structure. also pillow structures may form. these are spherical shapes in the rock. as a result the rock that forms the under part of the volcano is structurally weak.
once the volcano reaches sea level and above the rate of lava cooling is slower, the crystalline structure of the rock is better and the rock is stronger. as a result thee is a solid cap of rock on top of weaker rock beneath it. in places like Hawaii (above sea level) rock is prone to failure. if enough rock suddenly falls into the ocean a tsunami can be generated.

Question 29

how does a landslide or rockfall generate a tsunami?

Answer 29

movement of a large mass of rock down the flank of a volcano can create a wave.
landslides can also cause aa tsunami
the movement of a large mass of rock beneath or into the water can cause a tsunami

Question 30

what 2 factors control the formation of a tsunami by a rockfall?

Answer 30

the volume of rock that moves

the height that it falls from

Question 31

what is run-up height?

Answer 31

the elevation on land that the water reaches

Question 32

what is run-out distance?

Answer 32

the distance a wave reaches horizontally on land

Question 33

what is a trimline?

Answer 33

is the maximum height and distance reached on land by the wave as recorded by the damage done to vegetation, usually trees, by the water.

Question 34

describe the events that took place in Lituya Bay, Alaska, July 9, 1958

Answer 34

in this fiord an earthquake generated a large landslide from a mountain next to the ocean
upon impact with the water a 150 meter wave was generated.

Question 35

describe the events that took place on the Burin Peninsula, November 18, 1929.

Answer 35

on this date a large earthquake happened in the Gulf of St. Lawrence. as a result a large underwater landslide took place off the coast of Newfoundland near Burin Peninsula. this landslide created a tsunami that caused significant damage and the loss of 29 lives.

Question 36

what are tsunami-laid sediments?

Answer 36

a layer of sediment (a tsunami deposit) that is thinker and coarser (larger grains) near the coast and thinner and finer further inland.

Question 37

explain the earthquakes and tsunami hazard on the west coast of BC?

Answer 37

most large earthquakes originate under the Pacific Ocean off the West Coast of Vancouver Island. historically tsunami deposits are confirmed to those coastlines exposed to the Pacific Ocean. these deposits suggest a large earthquake with a tsunami occurs about every 300 years.

Question 38

what is a seiche?

Answer 38

a wave generated in an enclosed body of water that behaves like a tsunami. however, a seiche is wind generated not seismic

Question 39

what is a drainage basin?

Answer 39

the area of land drained by a river or river system.

Question 40

how does a typical drainage basin vary from its highest point to its lowest point?

Answer 40

Drainage divide, the high point of land that separates one basin from another

Question 41

how does a river erode, transport and deposit sediment?

Answer 41

1. weathering creates sediment

2. erosion in a river occurs because of the impact of moving water, impact of other moving sediment, and hydraulic lift

Question 42

there are 2 common types of river: 1) braided; and 2) meandering. what are some of the key differences between braided and meandering rivers?

Answer 42

Feature 		Braided		Meandering
# of channel		>1			1
Size of channels	Smaller		Larger	
Channel shape	High W/D ratio	Lower W/D ratio
Sediment Load	Coarse, Poorly	Fine, well sorted
			Sorted - moving	moving as suspended
			As bedload
Discharge 		Variable		Uniform

Question 43

what is discharge?

Answer 43

the volume of water moving in a river in a certain amount of time. 2 types of discharge: baneful discharge and base level flow

Question 44

what is balkfull discharge?

Answer 44

the maximum amount of water in the channel (often the dominant discharge)

Question 45

what is dominant discharge?

Answer 45

the volume of water in the channel that does the most work. work is measured by the amount of sediment that is moved ( often the bank full discharge)

Question 46

what is base level flow?

Answer 46

the minimum amount of moving water in a channel

Question 47

what is a flood?

Answer 47

is an event when there is more discharge then the channel can accommodate. this extra water leaves the channel and goes on to the flood plain

Question 48

what is a floodplain?

Answer 48

is the area of land next to the river channel used to store excess water temporarily and sediment longer-term.

Question 49

which river, braided or meandering is most likely to produce a catastrophic flood and why?

Answer 49

Braided river is more likely to create a more violet catastrophic flood because of faster moving water and quicker arrival time

Question 50

compare and contrast the behaviour of. braided river when it floods with that of a meandering river when it floods.

Answer 50

both rivers are capable of creating a catastrophic flooding event. a flood in a braided river may be more violent (faster water) but it will be shorter in duration.
a flood in a meandering river may be less violent (slower water) but last longer. also, a flood in a braided system will arrive quicker whereas in a meandering system it may arrive later after the precipitation event.

Question 51

explain the effects that frozen ground has on flooding.

Answer 51

permafrost makes the ground impermeable. precipitation is therefore quickly channeled into the river adding to a faster increase in Q. if there is flooding this excess water will remain on the surface making the flood worse

Question 52

explain the effects that saturated ground has on flooding.

Answer 52

when ground is saturated with water, any extra water will remain on the surface. As a result it will travel quicker into the river contributing to a more rapid increase in discharge.

Question 53

what is a hydrograph?

Answer 53

is a way to compare changes in river discharge over time

Question 54

explain the difference between a rural flood hydrograph and an urban flood hydrograph.

Answer 54

The urban hydrograph has a steeper rising limb compared to the rural as water enters the river quicker via gutters and drains, leading to a high peak discharge.The rural hydrograph has a more gentle rising limb compared to the urban hydrograph (and therefore a lower peak discharge) as some of the water does not reach the river as it is absorbed by the roots of the plants and then transpired out into the atmosphere

Question 55

describe in detail 3 floods control measures in common use. be sure to explain what they are, what they are intended to do and the impact they often have on a river system?

Answer 55

ARTIFICIAL LEVEES: raised banks of the river channel intended to increase the size of the channel and keep more water in it
ARTIFICIAL CHANNELS: extra river channels made to accommodate excess water and keep it moving
FLOODPLAINS: the large areas of land next to the active channel intended to store water temporarily.
all of these may alter the river system by either changing the size or shape of the channel, the # of channels, or the nature of the whole system including the flood plain

Question 56

what is a levee?

Answer 56

the raised portion of the flood plain next to the channel

Question 57

what are 3 ways that water can escape a river channel during a flood?

Answer 57

1. over top of the bank - once bank discharge is reached and exceeded water spills out of the channel over top of the bank
2. through the bank - water leaves through a break in the bank it is on avulsion
3. Underneath the bank as groundwater

Question 58

what is avulsion and what type of landform does it create?

Answer 58

when flood water leaves the channel through a break in the bank it is avulsion. the deposit thats created by a avulsion is a crevasse-splay. this is a fan shaped deposit that is thicker and coarser near the breach changing to thinner and finer away from the channel.

Question 59

what is channelization?

Answer 59

the modification of a natural river channel so as to control the flow of water in it. this may include straightening the channel. can also mean changing the banks and bottom of a channel

Question 60

what affect does channelization have on stream flow?

Answer 60

may straighten the channel, banks and bottom of a channel. this creates a rigid, fixed channel separate from the surrounding ground. Ground water cannot enter the channel nor can river water leave as groundwater.

Question 61

what affects do fire, logging and animal grazing have on stream behaviour?

Answer 61

fire, logging, and agriculture alter vegetation. most often this means vegetation is removed. once vegetation is gone there is nothing to intercept precipitation & nothing got keep this water from rapidly collecting on and moving across the land surface. more surface water means more sediment that eventually reaches the river channel. a large sediment load in a river can alter the river system

Question 62

what affect does streamed sand and gravel mining have on the behaviour of the stream?

Answer 62

sand and gravel -mining of a river bed changes the size and shape of the channel and the flow conditions in it

Question 63

what effect does stream flow have on a concrete pillar that has been placed in river channel?

Answer 63

as the water moves around the concrete post in the river turbulence increases and water velocity drops on the left side or down current side. the end result is erosion of sediment away from the front of the position and deposition.