Lecture Notes 1 Volcanoes Flashcards
Mount Saint Helens is a volcano in what state
Washington
What dates did Mount Saint Helens erupt
2004-2008 and in 1980
Which nation of Washington State referred to Mount Saint Helens as Si Yett (woman)
YAKAMA Nation
What is the legen of Mount Saint Helens
The mountain was a beautiful maiden placed on Earth to protect the bridge of the gods on the Columbia River from two battling brothers.
What are the names of the two battling brothers
Mount Adamsfd and Mount Hood. (Considered active and dormant)
What is a Volcano
An opening on the surface of the Earth
How many layers does the earth have and what are they
The earth has three layers.
They are the core (inner and outer)
The mantle
The crust
What does the outer core consist us versus the inner core
The outer core consists of molten rock and the inner core contains solid rock due to high pressures
What do volcanoes allow?
They allow molten or semi-molten rock known as magma to rise up from the lower portions of the earth’s crust and the upper portions of the mantle and erupt/escape onto earth’s surface
What four things does magma consist of:
1) liquified rocks (known as melt)
2) crystallized minerals
3) solid rocks (that are pulled into the melt)
4) dissolved gases (including water vapour)
Are magma and lava the same thing?
No
What is the difference between magma and lava
-Magma is molten or semi-molten rock beneath Earth’s surface.
-Lava is molten or semi-molten rock ON earth’s surface (its magma once it has erupted from the volcano
What can magma contain along with rock
Suspended mineral crystals and gases
What can lava contain along with the rock?
Other suspended minerals
What is the difference between oceanic and continental crust?
Oceanic crust is thinner but denser than the continental crust which is thicker but less dense.
What does the lithosphere consist of
Lithosphere is the upper portion of the mantle and the crust
What are the 4 spheres of the earth
Lithosphere, hydrosphere, atmosphere, biosphere
What is the hydrosphere
All water on or near earth’s surface (oceans, lakes, groundwater, aquifers, even water vapour in the atmosphere)
What is the atmosphere
The gases surrounding our planet and held in place by earth’s gravity.
What is the lowest region of the atmosphere called (where most gases are)
Troposphere
What is the biosphere
All living organisms on earth (mammals, birds, fish, fungi, bacteria, plants, etc…)
Earth’s entire crust and upper mantle can be subdivided into large rocky plates known as?
Tectonic Plates
What is the plate tectonic theory
Tectonic plates and their movements are employed to explain landforms, earthquakes and volcanoes.
The lithosphere is divided into how many major and how many minor tectonic plates?
7 major and 8 minor
What are the 7 major tectonic plates
North American Plate
South American Plate
African Plate
Eurasian Plate
Australian Plate
Pacific Plate
Antarctic Plate
What are the 8 minor tectonic Plates
Juan de Fuca Plate
Cocos Plate
Caribbean Plate
Scotia Plate
Arabian Plate
Indian Plate
Philippine Sea Plate
Nazca Plate
The lithosphere (ie: the tectonic plates it is made of) sit on the what?
Asthenosphere
What is the asthenosphere
It is the partially molten layer of Mantle
Why does the asthenosphere move
Due to heat transfer and rise and fall of partially molten rock within it
What happens when the asthenosphere below moves?
The tectonic plates are dragged along and move too
What are the three ways tectonic plates can move (due to asthenosphere)
Pulling away/split= Divergent plate boundary
Colliding= Convergent plate boundary
Sliding along one another= Transform plate Boundary
Depending on where the plate boundary lies, it can have different what? (2 things)
Thickness and densities (mass/volume)
Ocean crust is ______ and ______ than continental crust
Denser and thinner. Continental crust is thicker and less dense
Divergent plates are mostly found under what floors?
Ocean floors
What is a ridge?
A ridge is a long, narrow, raised part of the Earth’s surface (ex: long narrow mountain chains)
Volcanic activity and earthquakes are often encountered along ___ plates?
Divergent
What is the crest?
The sides of the ridge that slope away from the narrow top.
Divergent plates (like those found under the mid-Atlantic) result in the formation of?
Ridges
What is the result of divergent plates?
The formation of RIDGES
The mid-oceanic ridges measure how many km total all linked together? (Like one continual volcano)
60,000 km
What is volcanic activity
The release of magma onto earth’s surface
What percent of volcanic activity occurs under water, along mid-oceanic ridges
70%
What is a convergent plate boundary
When two tectonic plates collide
When an ocean crust plate and continental crust plate collides, which sinks below the other and why?
The ocean crust sinks below the continental crust due to its greater density
The sinking of one tectonic plate beneath another creates what?
Subduction zone
colliding tectonic plates are said to form what?
Convergent plate boundary
True or False: Convergent plate boundaries are home to many of the worlds most famous volcanoes and lots of earthquake activity
True
The sinking of one plate drags a lot of sediment into where?
Molten magma below
**Sinking one tectonic plate (which drags tonnes of sediment into the molten magma below) will do what?
Will alter the magma and results in a thick magma rich in silica (silicon dioxide)
Does the thick, gummy magma of volcanoes flow as easily once it erupts as lava?
No, it does not flow as easily because of the silica and it releases lots of gases in the process
What gases do volcanoes along subduction zones release? (Subduction zone= when one tectonic plate sinks beneath another)
H2O, CO2 and SO2
What is the shape of the volcano that comes with subduction zones (and therefore the thick magma) and WHAT IS THE NAME OF THIS VOLCANO
Tall, cone-shaped volcano known as STRATOVOLCANO
What kind of plate boundaries form stratovolcanoes?
CONVERGENT PLATE BOUNDARIES
Name three famous stratovolcanoes
Mount saint Helens (USA)
Mount Vesuvius (Italy)
Mayon (The Philippines)
What is a transform plate boundary
When tectonic plates slide along one another.
Wjat does the rubbing of two plates at transform boundaries result in? (And give an example)
Earthquakes due to built up stress caused when plates get stuck and subsequently manage to slide by one another.
Ex: SAN Andreas Fault along the Western USA
