Earth Science 104 Midterm #2

How are earthquake magnitudes determined?

1=10, 2=100, add 0, determined by ground motion and energy released.

how are tsunamis from earthquakes generated? how fast do they travel? do they just happen in one big waves or several?

800 kilometers/ 500 miles, several waves, they are generated from large, shallow earthquakes with an epicenter or fault line near or on the ocean floor

What is the difference between a subduction zone and a collision zone?

A subduction zone is a region of the Earth's crust where tectonic plates meet. A collision zone occurs when tectonic plates meet at a convergent boundary (continental lithosphere)

How are oceanic and continental crusts different?

Continental crust is less dense than oceanic crust, floats high on mantle, the mantle have different densities cause it is made of different kinds of rocks.

What type of plate boundary/ fault system caused the 2010 Hati Earthquake?

Convergent/ transform boundary (around hati) Slip strike (south american plate)

What is Isostasy?

Densities and thickness influence how high the crust is. The state of gravitation equilibrium between earths crust and mantle

What are the three kinds of plate boundaries? how do the plates move relative to each other at the different types of boundaries? Crust is created and destroyed at which ones? what types of land features are created at each? tallest features on the continents?

Divergent= pull apart convergent= pull together transform= rub each other divergent= plates move away from each other and lithosphere is created. convergent: plates move towards each other and lithosphere is destroyed. transform: plates slide past each other.

How did past flips in Earths magnetic field end up providing proof of seafloor spreading?

Earths magnetic field flips polarity overtime, minerals in hot lava line up with magnetic field. ,magnetic minerals freezes in place when lava turns solid.

What is the lithosphere? what is the asthenosphere? how do they differ?

Litho- brittle and breakable, crust and upper mantle cold. Asthenosphere- is a warm plastic later beneath the asthenosphere warm soft butter, (hard solid vs soft solid)

What are each of the major layers made of and what are their physical states?

Lithosphere- rigid outer shell, hard solid (granite and basalt rock) Asthenosphere- warmer plastic layer- soft, liquid silicate Lower mantle-Solid Inner core- (soft) solid, Iron Outer core- Liquid, Iron

What kinds of indirect evidence do we have regarding Earths composition?

Magnetic field (Iron core), gravity field (crust, mantle, core), seismic waves, meteorites.

What is seafloor spreading and why was it important to the theory of plate tectonics?

Plates diverge and move in opposite direction; rising magma fills the gap and a new plate of material is created

What kinds of direct evidence do we have regarding Earth's composition?

Rocks on surface (30miles), Drilling (10miles), Volcanic material (120miles)

What is Pangea?

Super continent that existed during the late paleozoic and mesozoic eras. it assembled from earlier continental units aprox 300 million years ago and began to break apart about 175 million years ago.

What is the relationship between earthquake locations and plate tectonics?

Tectonic Plates, Earthquakes, and Volcanoes. According to the theory of plate tectonics, Earth is an active planet. Its surface is composed of many individual plates that move and interact, constantly changing and reshaping Earth's outer layer. Volcanoes and earthquakes both result from the movement of tectonic plates.

What is a hotspot and how do we think they form?

The Hawaiian islands form as the pacific ring of fire and the plate hides over plume of hot mantle

What is continental drift, and how is it related to plate tectonics?

The gradual movement of the continents across the earths surface through geological time.

What drives the the tectonic plates?

Theory is that convention within the earths mantle pushes the plates in.

Are earthquakes the only reason we can have tsunamis?

Volcanic eruptions, underwater landslides, meteoroids

Which plate boundaries have volcanos? earthquake? both?

Volcanoes= hot spots/ divergent/ convergent. Earthquakes= divergent/ mid-ocean ridges

When the Earth formed, it was homogeneous, but now it is layered-explain how this occurred?

When it formed the lighter parts (like continental crust) floated to the surface, and the really heavy parts (like iron and nickel in the core) sank to the middle

How fast do tectonic plates move?

about 2 to 5 cm per year (1-2 inches)

What type of plate boundary/ faults system caused the 2010 Chile earthquake and the 2011 Japan earthquake?

convergent= chile (nazcra plate). Japan= (north american plate)

what is the evidence for a very large earthquakes in pacific NW, when was the last one and how often do they occur?

dead forests= coast line drops down, new soil develops above the old alternating layers of sand and mud indicate large earthquakes

What are some real world examples of divergent boundaries (both continental and oceanic)? Examples

divergent= eurasian plate/north american plate. Convergent= south american plate/ nazaca plate. transorm= san andreas fault

How and where did the Yellowstone hotspot first appear? what evidence do we have of that?

melts its way through plate capped by thick continental crust. the continental hotspot/ volcano like a lava lamp! there are giant explosives

what are the types of earthquake waves we covered in class and how can they be used to determine earthquake location?

p and s waves. the p waves have a push pull compressional motion and travels through solid/liquid gases. the s waves which are secondary waves, has a shake motion and only travels through solids, slower than p waves

What observations led to the theory of continental drift? what were its problems?

shorelines match up with the materials and fossils distribution.

What is meant by the plate tectonic "conveyor belt"?

subduction carries plates into the mantle, the material lost is balanced by the formation of new oceanic crust along divergent margins by seafloor spreading the total surface of the globe stays the same.

What is an earthquake?

the epicenter is the point on the earths surface vertically above the focus point in the crust where an earthquake happens. focus is where the earthquake begins. focal depth is how deep the earthquake is

How does the age of the seafloor change as you move away from a seafloor spreading?

the youngest is towards the middle of oceans, older towards the edges. crust moves away from ridges as oceans widen.