Dynamic earth/minerals Flashcards
When did geological time start
When the first solid material condensed in our solar nebular. These solids accreted over and over forming planetesimals which then formed planets
What is the principle of uniformity
The present is key to the past. The earth has always changed in uniform ways.
What is the principle of superposition
The layers of sedimentary rock, the oldest is at the base and the layers get progressively younger in ascending order.
What is the principle of original continuity
Sediments generally accumulate in continuous sheets. If you see a sedimentary layer cut by a valley, one can assume that the layer once spanned the valley and has been eroded by the river that formed the valley
What is the geological column
By correlating rocks for all around the world geologists have pieced together a stratigraphic column that represents the entirety of earths visible history. Define the course of life’s evolution through life’s history.
What is relative/numerical age
Relative= The age of one feature relative to another
Numerical= age of a feature in given years.
What is radioactive decay
Converts an element into a different one. Rates are commonly stated in terms of half life (time needed for half a group of isotopes to decay
What is geochronology
Investigation of what, when and how of planetary scale processes.
Seismic waves, discuss
Rupture of intact rock or frictional slip along a fault produced them. Move outwards in all direction . P and S waves. To travel through material, and on velocity at which this occurs depend upon the character of that material,
what is a mass extinction
A mass extinction is a relatively sudden, global decrease in the diversity of life forms. To be a mass extinction, the following must occur:
* Extinctions occur all over the world.
* A large number of species go extinct.
what is the speed of seismic waves proportional to
rock density
what speeds with P-waves travel at
8 km/sec in dense igneous rocks (e.g. peridotite) but 3.5 km/sec in sandstone
which do seismic waves travel faster in
faster in solids than liquids – so more slowly in magma than solid rock
what type of wave can’t travel through liquids
S-waves
when will seismic waves as energy reflect/ refract
when reaching the interface between two layers of rock of differing compositions and/or densities
what concept enabled the discovery of the crust/mantle boundary in 1909
reflection/ refraction
what depth is the crust-mantle boundary
35-40 Km
what % is the atmosphere of the planets mass
0.03%
what % is the crust of the planets mass
0.47%
what % is the mantle of the planets mass
67%
what are phase changes
levels at which atoms are rearranged and packed more closely
at 410 km what happens to olivine
unstable and collapses to form denser magnesium spinel
what is the shadow zone
S-waves can’t pass through the liquid core and therefore are not recorded
what happens to P-waves at the core
The unrefracted wave passes directly through the core, emerging at C.
But it reaches C sooner than predicted if the entire core is liquid, i.e. it travels too fast for that possibility – hence an inner part must be solid
