Ch 3 - Our Fascinating Earth Flashcards
What do we call the study of the earth and its structures?
geology
What do we call scientists who study the structure of the earth?
geologists
What do we call the outer layer of the earth?
the crust
What do we call the boundary between the crust and the mantle?
the Moho or Mohorovičić discontinuity
What do we call the innermost region of the earth?
core or inner core
What is made up of a mixture of broken-down rocks and decomposed plants and animals
soil
By what process is new soil formed?
weathering
What type of weathering is caused by ice, flowing water, or windblown sand?
physical weathering
What do you call underwater mountain ranges where plates of the earth’s crust are thought to be moving away from each other?
mid-oceanic ridges
What kind of weathering is caused by natural acids slowly eating into a rock and breaking it apart?
chemical weathering
Describe the earth’s mantle.
- 2,900km thick
- makes up the largest portion of the earth’s interior
- it is very hot, and temperature increases with depth
- the rocks are weakened by the heat so that they slowly flow under pressure like warm plastic
Which part of the earth’s core is a solid and which part is liquid?
The inner core is solid and the outer core is liquid.
Name the three main sections of the earth labelled below.
- crust
- mantle
- core
Describe the earth’s crust.
- outermost layer of the earth
- quite thin compared to the size of the earth
- much is covered by soil, sand, and other sediment
Describe the earth’s core.
- innermost region of the earth
- divided into two sections: inner and outer core
- made up of metals rather than rock
What are giant waves caused by earthquakes called?
tsunamis
What is the shaking or trembling of the earth’s crust called?
an earthquake
What is the study of earthquakes called?
seismology
What are scientists who study earthquakes called?
seismologists
What do you call the break that appears at the boundary between two moving masses of rock?
a fault
What do you call the point under the ground where an earthquake begins?
the focus
The strength of an earthquakes is called its…
magnitude
The regions of the earth’s crust where most earthquake faults are found are called…
seismic belts
In which region do most earthquakes occur?
the Circum-Pacific Belt
What do you call the place at ground level that is directly above the focus of an earthquake?
the epicentre
What scale is used to measure the strength of an earthquake?
the Richter scale
How can the motions of the earth’s plates cause earthquakes?
Sometimes the edges of moving plates become stuck and cease to move, allowing huge forces to build up. The force may eventually become so great that the plates suddenly break free and slide against each other for several seconds, producing an earthquake.
What do you call melted rock that is still underground?
magma
What do you call a reservoir of magma a few miles beneath the surface that may give rise to a volcano?
a magma chamber
What do you call a vent that allows molten rock and hot gases to escape from within the earth?
a volcano
What do you call an opening in the ground through which a volcano erupts?
a vent
What is the name given to melted rock that has reached the earth’s surface?
lava
What name is given to the belt of volcanoes that encircles the Pacific Ocean?
the Ring of Fire
What do you call holes or cracks serving as escape vents for underground gases?
fumaroles
Lava fragments that solidify into rock fragments almost immediately are called…
tephra
What is volcanic ash?
the smallest fragments of tephra, resembling dust or fine sand
What is lapilli?
fragments of tephra that are smaller than bombs or blocks but larger than volcanic ash; means little stones
What is the depression at the top of a volcano called?
a crater
What is a caldera?
a huge bowl-shaped depression formed when an empty magma chamber collapses after a volcanic eruption
What is an active volcano?
An active volcano is one that has erupted recently or is considered likely to erupt in the near future
What is a dormant volcano?
A dormant volcano is one that erupted many years ago and is now inactive but may erupt again in the future
What is an extinct volcano?
An extinct volcano is one that has not erupted in recorded history or is unlikely to ever erupt again
What type of volcano (below) is dome-shaped and formed by eruptions of fluid, runny lava that build up gradually? (The Hawaiian Islands were formed by this type of volcano.)
shield volcano
What type of volcano (below) is relatively small, cone-shaped, formed mostly of tephra, and quickly eroded? (Paricutín is an example.)
cinder cone volcano
What type of volcano (below) is steep-sided and formed by alternating layers of fluid lava and tephra? (Mt. St. Helens is an example.)
composite volcano
Describe a Hawaiian eruption.
The volcano produces a high amount of fluid lava that surges from the vent like water from a fountain. If it gushes from a narrow vent it may shoot in the air, and if it erupts from a long crack it may form a sheet-like fountain called a fire curtain. It can also pool within the vent to form a ‘lake’ of lava.
Describe a Strombolian eruption.
Strombolian eruptions are noisy but mild, with globs of hot lava flung into the air where they harden into volcanic bombs.
Describe a Plinian eruption.
Hot clouds of gas and dust are expelled high into the air, usually quite violently. The ash clouds that form can travel completely around the world.
What do we call the huge pieces of the earth’s crust that “float” like rafts on the upper mantle?
plates
What are three different types of tephra?
volcanic ash
lapilli
volcanic bombs
What are volcanic bombs?
Volcanic bombs are fragments of tephra that are more than 2.5 inches across. Some may be several feet across!
