Volcanoes & Magma
What is magma?
A molten mixture of rock forming substances, gases, and water.
What do scientists use to "see" the interior of the earth?
Earthquake waves (seismic waves) - specifically S- and P-waves.
What are the 3 types of stress Earth's crust experiences?
Tension, Compression, and Shearing.
Where is sea floor the oldest? the youngest?
Oldest by the continents, youngest in the middle.
What are the two types of plates?
Oceanic plates and continental plates
Why does magma rise to the surface?
It is less dense than the surrounding rock.
Describe the asthenosphere.
The asthenosphere is soft and plastic like, and is the layer that allows the continents to move.
What is an earthquake epicenter?
The location on the surface of the earth directly above where the earthquake happened.
Where is the sea floor the hottest? the coldest? Why?
Hottest in the middles, coldest by the continents, because there are volcanoes along the middle.
What landforms occur at convergent plate boundaries?
Mountains, volcanoes, oceanic trenches
What is viscosity?
Viscosity is the resistance of a liquid to flow.
Where does Earth's internal heat come from?
Radioactive substances breaking down.
What is an earthquake focus?
The area underground where the earthquake actually happens.
Where did scientists look to find proof of sea floor spreading?
Mid ocean ridges.
What is subduction and where does it occur?
Subduction is when an oceanic plate gets pushed under another plate (continental or oceanic), and sinks into the mantle. It occurs along plate boundaries.
What does the viscosity of magma depend on?
Silica content and temperature
What causes convection currents inside the earth?
Heat from the outer core.
What are the three types of seismic waves, and in what order do the waves reach a seismograph?
P-waves, S-waves, and Surface waves, in that order.
What technology did scientists use to determine the sea floor was spreading?
Sonar
What is a rift valley and where do they form?
A rift valley is a valley created by a continental plate being pulled apart by forces in the earth's crust. They form at divergent plate boundaries on land.
What is a stratovolcano?
A volcano shaped like a large cone, and formed from alternating layers of lava and other rock types.
Define convection.
Convection is the transfer of heat through the movement of fluids - liquids or gases.
Which type of stress causes reverse faults?
Compression, Tension, or Shearing?
Compression.
Who was the scientist that discovered that the oceans were shallowest in the middle and deepest near the continental margins?
A. Alfred Wegner
B. Robert Oppenheimer
C. Henry Hess
D. Isaac Newton
Henry Hess
What is ridge push and slab pull, and where do each of them occur?
Ridge push is the force created from new material being generated at mid ocean ridges, slab pull is the force created by the sinking part of subducting oceanic plates.
Ridge push occurs at mid ocean ridges, slab pull occurs at subduction zones.