Earthquakes & Volcanos Flashcards
What is a volcano
A volcano is a conical hill or mountain formed by material from the mantle being forced through an opening or vent in the Earth’s crust.
What are active, dormant and extinct volcanoes?
Volcanoes are found in three states - extinct, dormant and active. An extinct volcano will never erupt again. A dormant volcano has not erupted in 2000 years. An active volcano has erupted recently and is likely to erupt again.
What are the different types of volcano?
Composite
Shield
Dome (Acid lava cones)
Composite volcanos
Composite volcanoes, sometimes known as strato volcanoes, are steep sided cones formed from layers of ash and [lava] flows. Composite volcanoes can rise over 8000 feet. Examples of composite volcanoes include Mount St Helens (USA). They are very explosive.
Shield volcanoes
Shield volcanoes have gently sloping sides and are formed from layers of lava. Eruptions are typically non-explosive. Shield volcanoes produce fast flowing fluid [lava] that can flow for many miles. Examples of shield volcanoes include the Hawaiian volcanoes. Although these eruptions destroy property, death or injury to humans rarely occurs.
Where are volcanoes located?
Volcanoes are found along destructive (subducting) plate boundaries, constructive (divergent) plate boundaries and at hot spots in the earth’s surface.
What is the Ring of Fire?
The ‘Ring of Fire’ is a volcanic chain surrounding the Pacific Ocean. It is formed along a destructive (subducting) plate boundary.
Earthquake
a sudden movement of the earth’s surface
Conservative Boundary
where two plates move alongside each other - although crust is neither created or destroyed here, earthquakes usually occur here.
Destructive Boundary (Convergent)
where two plates move towards each other - in the case of a plate consisting of continental crust meeting a plate consisting of oceanic crust, the oceanic crust will be subducted and destroyed as it is less dense.
Constructive Boundary (Divergent)
where two plates move away from each other resulting in new crust being formed.
Collision Boundary
where two plates of continental crust move towards each other creating fold mountains
What is a Plate Boundary?
The point where two or more plates meet is known as a plate boundary.
What are fold mountains?
Fold mountains are mountains formed from the folding of the earth’s crust.
foreshock
a small earthquake before a large one
joint
a crack in a rock
lava
molten rock at the Earth’s surface
lahar
mudflow triggered by a volcanic eruption
pyroclastic flow
a cloud of superheated gas and ash ejected from a volcano
volcanic bomb
lava exploded into the air which solidifies as it falls
Continental Drift
Continents drifted to their current locations.
What are the effects of volcanoes?
they kill people, destroy property, and disrupt the environment
Where do volcanoes tend to erupt more violently?
convergent boundaries
What forms acid rain?
sulfurous gases from volcanoes
What is the difference between focus and epicentere
focus=where the earthquake actually originated/started
epicentre =where the earthquake actually started/originated directly above it on the earth’s surface
What is the difference between volcanic eruptions and earthquakes?
earthquakes are caused by transform boundaries and volcanic eruptions are caused by convergent boundaries
Explain the operation of a seismograph.
3 measuring instrument for detecting, locating, and measuring the intensity and direction and duration of movements of the ground - weighted pen
Where do earthquakes occur most often?
along plate boundaries
Earthquake Risk
- Falling Objects- main cause of injuries in earthquakes
- Structure Failure- Due to the shaking and ground movement in all directions. Few structures can withstand side to side motion.
Earthquake Risk Part Two
- Fire and Electricity- gas lines breaks, fires happen. Power lines fall.
- Tsunamis- where a slab of ocean floor is vertically displaced along a fault, when an underwater landslide is triggered by a quake.
Richter Scale
Measures earthquake intensity and the amount of damage caused by an earthquake
How is an epicentre located?
locating the epicentre help geologists identify areas where earthquakes may occur in the future. Geologists use seismic waves to locate an earthquake’s epicentre. they use data from thousands of seismograph stations set up all over the world.
How are buildings and homes designed to be earthquake resistant?
These are known as seismic-safe buildings. Reinforcing buildings with shear walls, tension ties, base isolators, cross braces, dampers, and flexible pipes. In houses the bookshelves, cabinets, and tall dressers are fastened to the wall, the house is bolted to its concrete foundation, the chimney is secured with metal brackets and plywood is nailed around it, beds are away from the windows and heavy objects are no above the bed, plywood panels strengthen the walls, metal connectors strengthen the house’s frame, and water heaters are strapped to the wall. New buildings are made stronger and more flexible, old buildings must be modified to withstand stronger quakes.
What is the earths crust?
Earth’s outermost layer
epicentre
Point of Earth’s surface directely above an earthquake’s focus
Focus?
in an earthquake, the point beneath Earth’s surface where energy release occurs
inner core?
very dense, solid centre of the Earth
magnitude
measure of the energy released by an earthquake
mantle?
largest layer inside Earth
outer core?
liquid core that surrounds Earth’s solid inner core, and that is made mostly of iron
seismic waves?
energy waves that are produced at and travel outward from the earthquake’s focus
seismograph?
device used to record primary, secondary, suface waves from earthquakes
tsunami?
powerful seismic sea wave that can travel thousands of kilometers in all directions and that begins over an earthquake focus
Fault?
surface along which rocks break and move
