Lab 1

Question 1

How are Plate Boundaries categorized

Answer 1

Plate boundaries are categorized by the relative motion between the two plates at the boundary (convergent, divergent, or transform), and by the material the two plates are made of at the boundary (continental or oceanic crust).

Question 2

what are Ocean-Ocean divergent Boundaries

Answer 2

Boundaries where two oceanic plates separate
Ocean-Ocean divergent boundaries are called sea floor spreading ridges. They are common. Ex Juan de Fuca and Pacific Plate

Question 3

what are Ocean-Continent Divergent Boundaries

Answer 3

Boundaries where an Ocean diverges from a continental plate
Ocean-continent divergent boundaries are very rare

Question 4

What are Continent-Continent Divergent boundaires

Answer 4

Boundaries where two continents are separating
Continent-Continent divergent boundaries are Rare, such as East African Rift Valleys

Question 5

what are Ocean-Ocean convergent boundaries

Answer 5

Boundaries where two Oceanic plates are pressed into each other
Ocean-Ocean convergent boundaries are common, such as the subduction at the Aleutian Islands, Pacific and North American Plates

Question 6

what are Ocean-continent convergent plate boundaries

Answer 6

Boundaries where an oceanic plates is pushed into a continental plate
Ocean-Continent convergent plate boundaries are common. They are coastal subduction zones such as between the Juan de Fuca and North American Plates

Question 7

what are Continent-Continent Convergent boundaries

Answer 7

Boundaries where Continental plates push into another
Continent-Continent Convergent Plates are Uncommon. Examples of them are the Himalayas, Australo-Indian and Eurasian Plates

Question 8

what are Ocean-Ocean transform boundaries

Answer 8

Boundaries where an Ocean plate slides past an Ocean plate
Ocean-Ocean transform boundaries are common. It includes all the offsets of the sea floor spreading ridges

Question 9

what are Ocean-Continent transform boundaries

Answer 9

Boundaries where an Ocean slides past a Continent
Ocean-Continent transform boundaries are Uncommon

Question 10

what are Continent-Continent transform boundaries

Answer 10

Boundaries where a continent slides past another continent
Continent-Continent transform boundaries are Uncommon, includes examples like the San Andreas Fault system between the Pacific and North American Plates.

Question 11

What are all the types of plate tectonic boundaires

Answer 11

Divergent: (Ocean-Ocean, Ocean-Continent, Continent-Continent)
Convergent: (Ocean-Ocean, Ocean-Continent, Continent-Continent)
Transform (Ocean-Ocean, Ocean-Continent, Continent-Continent)

Question 12

What is the Seismic Activity at Divergent Boundaries

Answer 12

Divergent Boundaries can cause shallow, mild to moderate intensity earthquakes. This is because the Crust is being thinned and pulled apart which doesn’t build up much elastic strain.

Question 12

What is the Seismic Activity at transform Boundaries

Answer 12

Transform Boundaries causes shallow earthquakes but can have more significant magnitude due to the elastic strain that builds up from the plates scraping against each other.

Question 13

What is the Seismic Activity at Convergent boundaries

Answer 13

Convergent Boundaries involving Ocean Crust can cause Shallow to Deep earthquakes that can be minor to the strongest known earthquakes. Caused by significant elastic strain along the boundary. Oceanic trenches and significant explosive volcanism are also associated with these boundaries

Question 14

what is the seismic activity at Continent-Continent convergent boundaries

Answer 14

Continent-Continent convergent boundaries can cause dominantly shallow earthquakes from the intense collision of two continents

Question 15

what is the seismic activity at mantle plumes

Answer 15

Mantle plumes are the rise of large volumes of hot buoyant magma within plates. Upwards pressure of these plumes can cause stretching and cracking of the overlying crusts. Dominantly shallow and lower intensity earthquakes.

Question 16

what is the Epicentre and Focus of an Earthquake

Answer 16

Earthquakes occur when the rigid lithosphere breaks due to accumulated strain and releases the stored energy. The energy radiates in all directions from the source of the earthquake (called the focus) in the form of seismic waves. The Epicentre is the point on Earth’s surface directly above the focus.

Question 17

what are the three types of seismic waves

Answer 17

There are three types of seismic waves. P (primary), S (secondary), L (surface). They are all released at the same time, but travel at different speeds and through different materials.

Question 18

what are seismograph instruments are Seismograms

Answer 18

Seismograph instruments amplify and record the ground motions produced by passing waves. The resulting seismograms are then used to determine the time and location of an earthquake

Question 19

what data is given in the upper right corner of a seismogram

Answer 19

The first three letters in the upper right give you the station code of the seismogram. Below is the date of the earthquake, and finally the time the seismogram paper is started. It is listed in hh:mm:ss.sss format. The X axis is seconds.

Question 20

what are the three steps to finding the distance an earthquake is away from a seismograph station, along with its location

Answer 20

1. Find the times the P wave and S waves arrived. These will be called P arrival and S arrival. P is the first wave that arrives, S is the second, usually stronger one.
2. Subtract these numbers to get the S-P interval. Use the supplied seismic Wave Travel Time Graph to convert time in seconds to the distance the earthquake is from the seismograph.
3. If you are trying to find the location of the earthquake epicentre, do the same process for three different stations, then draw circles with the radius being distance from the station centred on the station, where all three circles intersect is the epicentre.

Question 21

How do you determine when an Earthquake occurred from a seismogram

Answer 21

1. Use the distance that was determined as the distance from the earthquake epicentre to the location of the station. Use the same Seismic Wave travels time graph to determine how long it takes a P wave to travel the determined distance.
2. Subtract P arrival by P travel. This get times in seconds, which can be plugged into the time the graph started. If the seconds were over 60, it can then be adjusted by adding a minute and subtracting 60 seconds.

Question 22

what is the plate setting off of the west coast of Vancouver Island

Answer 22

A convergent Margin off the west coast of Vancouver Island is where the 7km thick Juan de Fuca plate subducts under the 20-40 km thick Continental plate of North America. They approach at 4-7 cm/yr.

Question 23

What are Ocean-Ocean divergent boundaries like

Answer 23

Have infrequent weak volcanism, mostly shield
Have fairly common weak and shallow earthquakes
Are found at a broad shallow area of the sea floor with small ridge at the centre
Youngest rock nearest to ridge, gets older further out

Question 24

what are ocean-ocean convergent boundaries like

Answer 24

Frequent strong volcanoes, strato common, other types too Frequent earthquakes that range from low to high magnitude and shallow to deep Mountainous island chain on one side with a Deep trench on the other side. No pattern with sea floor age

Question 25

What are Ocean-Continent convergent boundaries like

Answer 25

Frequent strong volcanoes. Mostly strato and caldera. Others too though Frequent strong earthquakes, shallow to deep Form a coastal mountain chain often with a deep trench on other side. No pattern of sea floor age

Question 26

What are Continent-Continent convergent boundaries like

Answer 26

Not much volcanic activity Lots of earthquakes, can be strong. Mostly shallow, some deep Forms very high mountains and plateaus.

Question 27

What are Ocean-Ocean transform boundaries like

Answer 27

little to no volcanoes (some nearby, but caused by spreading ridges) common earthquakes, but always shallow, lot to moderate magnitude can see the offset of spreading ridge right at the transform boundary Age of sea floor data shows the offset of the transform faults very clearly