Big picture: 15 by ago...
Big bang, then stars which live for about 10 BY, then...
Nova, supernova, neutron stars
4.5 by ago-solar system (including bits from supernovae)
When first stars die as supernovae (about 10 BY into their life), the heat and pressure created all elements beyond Iron on the periodic table
Anything on our planet that is lower than Iron on the periodic table, came from the explosion of an older star, including stuff inside YOU.
Earth forms from molten elements as our solar system is formed, (called an accretion disc) including Uranium
(reason for heat still in the core-see the minister estimate of Sunday afternoon creation date)
Geo time: ("deep time")
You can look up the K-T extinction online, it happened 65MY ago. Look up the dude that discovered it...
See videos: How the earth was made...
Layers: (onion boy)
Core-Mantle-Crust-think of an apple
Core is actually two bits: solid inner iron and nickel, liquid outside that bit. It spins, giving us a weak magnetic field
How do we know this? Nuclear bomb testing and our global seismic sensor network
Hint: the inner part spins around in the opposite direction every 60-80 MY, so the earth's magnetic field actually FLIPS (this is important for later-or sooner)
Plate Tectonics-look up this guy: Wegener. Meteorologist (weather guy), so the geo folks laughed at him...
Asthenosphere-"sticky rock" (from Greek ἀσθενής asthenḗs 'weak' + "sphere")
Lithosphere-floating rock (litho = stone) (Ancient Greek: λίθος [lithos] for "rocky", and σφαίρα [sphaira] for "sphere")
Continents-even more floaty, made of lighter rock (granite) that formed from interaction of magma with oceans
Plates are large, float on the Asthenosphere
Continents are like rafts on the Asthenosphere, more buoyant than the plates
The plates can slide under each other (subduction zones), crash into each other (Himalayas), next to each other (transform faults), and are formed at spreading zones (divergent boundaries)
Check out this diagram: note the red (spreading) and the blue (subducting), esp. look at Chile---->
What mountains are in Chile?
Volcanoes are the key:
Two kinds of volcanoes: Andesitic (pointy), Basaltic (runny, look out your window)
Andesite-from pressure and heat as plates subduct (sticky, high silica content, e.g. Andes mountains)
Basalt-from ocean crust, lots of water, makes for weak, runny magma, formed as magma pushes through watery ocean plates
Note the sticky stuff boiling up in red-this is why the Andesitic volcanoes are sticky, and always found near subduction zones (Andes, Cascades, Japan, Italy, etc.)
Note also the trench where the subduction zone goes down: this is the origin of the Chilean/Peruvian trench we covered in the El Nino notes, as well as the deepest part of the ocean: the Marianas Trench, which is 7 MILES deep. Whoa!
Historic data shows subduction zone quakes that would create a tsunami 1000' high or more on the pacific northwest coast, flooding everything west of I-5.
Look at all of the earthquakes (red dots) as the plate subducts
Two things to take-away about subduction zones:
1. subduction zones create ANDESITIC (pointy) volcanoes, which are high in silica, and sticky like thick pancake batter.
2. subduction zones create lots of deep focus earthquakes.
--See the submarine notes
What the heck is this?
Note the symmetry along the ridge crest. This was mapped in WWII in an attempt to detect metallic submarines using magnetic sensors on ships. Later on airplanes like this:
You will see these practicing at the Kona airport, look out for them. They are spying on submarines. Not ours.
Remember the earth magnetic field changing?
Usually in the middle of an oceanic plate, but can also be mid continent (e.g. Yellowstone supervolcano caldera)
Hot spots-basalt-low silica content, melts easier (e.g. look out the window)
Look at the Hawaii island chain on google earth (underwater version)
While you are at it, look for the Nuuanu landslide that created a 4000' tsunami
You can also look at the Mauna Loa simulated tsunami on youtube...
then there's the famous "notmy" fault...
Epicenter is the place ON THE SURFACE above the hypocenter (true origin) or earthquake FOCUS. Deeper hypocentric quakes often feel "longer", while shallow hypocentric quakes feel "sharp".
How do we find these?
P waves travel by compression (comPression). These are longitudinal waves, like sound. They can travel through liquid or solid.
S waves travel by shear (Shear). These are transverse waves, like a slinky. They can only travel through solids.
This is how we know what the inside of the earth looks like:
This data was found by spying on atomic bomb tests in the 1950's, not because we wanted to know about the guts of our planet...
Ok, back to earthquakes.
Suppose you have a house on posts (called "post and pier" construction). An earthquake happens some distance away. First your house moves back and forth (P wave, much faster at 8 km/sec). After a time, your house bounces up and down from the S waves (slower at 3 km/second).
If you are far away, these are separated by different arrival times.
If you are near the epicenter, they hit at the same time...up, over, down=your house is demolished
We use this difference to calculate distance from the epicenter (and hypocenter if you are interested) using delay times on the seismograph
Look at the HPA seismograph here:
and our Hawaii quakes here:
Click on some earthquakes and note the depth and the seismic image.
Next: Rocks Module 25
Metamorphic (Kafka rocks, just kidding: changed by heat and pressure)
Igneous= directly from magma, can be either basalt (low melting point, like our island or oceanic plates) or granite (lighter, what continents are made of)
Granite breaks down into light colored sand, makes for fertile soil. Basalt (like us) can make sand too, but less fertile (e.g. black sand beach).
Sedimentary= just like it sounds, from mud, sand or dust, usually in layers.
Metamorphic= changed by heat and/or pressure (slate, marble or coal)
Soil-formed by weathering (chemical or physical) of parent rock
Erosion can be by water or air (wind)