stress is the force per unit area applied to Bending a piece of solid object

geolegical stress regimes

• extensional (normal faults)
• compressional (thrust and rdeverse)
• strike-slip

stratigraphy

How do we understand what different stratum look like for historical dating, etc.,

uniformtarianism

“the past history of our globe must be explained by what seems to be happening right now.”

• an unconformity: a gap in the stratographic record
• if you look at the layers of the earth, if the lower older layers is not flat but the top layers are flat, then the lower layers have been squeezed / deformed in time

basic principles

• superposition: lower is older
• original horizontal: original is flat, tilt is later
• original continuity: if there’s a hole, it was a block before and something cut it
• cross-cutting relationships: if something cuts another thing, the thing that cuts it must be younger

unconformities

if there is some point where there’s a “sharp turn”, we call that an unconformity.

Energy in

Solar energy comes in from the sun. Heat flows out from the deep interior.

• sun’s luminosity changed by 25% over 4B years
• “faint young sun paradox” (“sun is actually dimmer before.”)

Sun spots have an ~11 year cycle, resulting in 0.1 -> 0.2 global temperature change.

Milankovitch Cycles

The eccentricity of the Earth’s cycle wrt sun has increased (cycle become more ovoid).

precession

the axis wrt the earth’s self rotation is slightly rotating

metamorphism

Metamorphism: protolith + heat and pressure => changes in the mineral composition / orientation in solid states until energy-minimizing state “comfortable with each other and their surrounding.”

Given 25 deg C per KM, we know only 250-850 deg c is required for it: so, only need about 10km required for metamorphism.

protolith

starting point of the rock, from shale, etc.

why heat?

Heat causes atoms to vibrate rapidly: stretching, bending, breaking chemical bonds. Atoms detach from neighbors, form new bonds with more stable different atoms.

There’s So Much Oil in the Ground

oil

“Fossilized Sunshine” photosynthesis => plant elements => preserved sedimentary rocks.

• small critters
• phytoplankton
• plant matter

maturation process

Carbon-rich organic features, deposited. Increased pressure. Eventually compressed into…

kerogen

A solid, seminary rock that’s carbon rich. With enough pressure, carbons join up and then you get a chain.

Oil: C16H34, C7H16 etc.

increase pressure

….oil gets squeezed out from the kerogen, and then density differences makes it rise.