1st Periodical

*Other info basahin niyo na lang because im tinatamad na

Evidence of Plate movement: pg. 74

Disasters and Preparedness Shz: pg. 38

Volcano: pg.41

PLATE TECTONICS THEORY

- explains the processes that cause formation of different geological features and phenomena

- states that Earth's lithosphere is composed of fragments/plates that move around and interact with one another

Tectonic - tectonicus (Latin) tektonikos (Greek), meaning "to build"

Supercontinent - PANGAEA

250 million years ago - began to break apart

Plate tectonic - is a movement of plates is brought about by the interaction of great forces that has resulted in the formation of various surface features of the Earth

The theory of plate tectonics originated in the late 1960’s by combining two pre-existing theories:

1. Continental Drift

– The idea that continents move freely over the Earth’s surface, changing their positions relative to one another

- set forth in 1912 by Alfred Wegener: German meteorologist and geophysicist, father of the plate tectonics theory(modern ver. of continental drift theory he proposed)

2. Sea-Floor Spreading – A hypothesis that the sea floor forms at the crest of the mid-oceanic ridge, then moves horizontally away from the ridge crest toward an oceanic trench

EVIDENCE OF PLATE TECTONICS

1. Jigsaw fit, Matching Continents: Continents can be made to fit together like pieces of a jigsaw puzzle; the idea that continents were once joined together, and have split and moved apart has been around for more than 130 years

2. Mountain Belts: Rocks of similar type, formation and age have been found in South Africa and Brazil.

*Mountain ranges and fold belts all become consistent if the modern day continents are fitted back into the Pangean landmass (e.g. the mountains of northwest Europe correspond geologically with the Appalachians of the USA).

3. Fossil Evidence: Certain identical rare fossils have been found in different continents, now separated by vast oceans.

*A plant which existed only during coal-forming times has only been found in India and Antarctica.

*Coal (which forms under warm, humid conditions) has been found under Antarctica.

*Limestone, sandstone and coal found in Britain could not have formed under its current climatic regime.

LAYERS OF THE EARTH

1. Crust - divided into 2: continental and oceanic crust

*Lithosphere - ball of stone; outermost layer of the Earth; made up of crust and top-most portion of the mantle

a. Continental Crust - made of granite & andesite rocks (easier to stay above the asthenosphere), thicker and less dense, ave. density of 2.7 g/cm^3

b. Oceanic Crust - crust under an ocean; made of basalt (thin but has high density, tends to float below the asthenosphere), ave. density of 3.0 g/cm^3

2. Mantle - thickest layer and makes up about 84% of Earth's volume; 2,900 km thick; mass of 4.01 x 10^24 kg contributing to 67% of the total mass of Earth

*Asthenosphere - between crust and mantle; partially molten (not liquid) layer of the mantle on which the lithosphere moves

*Mesosphere - below the asthenosphere and above the outer core

a. Upper mantle - solid region; composed of Iron, Oxygen, Silicon, Magnesium, Aluminum

b. Lower mantle - solid rocks; composed of Iron, Oxygen, Magnesium, Aluminum

3. Core - ball-like core, hot & dense

*Outer core - 2nd largest layer; composed of super heated molten lava of liquid iron & nickel; 4,000-5,000 Celsius; responsible for the magnetic field generation of Earth

*Inner Core - very hot and dense and heavy iron and nickel material

Deformation of the Crust - the changing of Earth's surface caused by tectonic forces that accumulated in the forest

Diagram of Stress (too much pressure) in Earth's Crust

Tension - stretches rock

Compression - pushes rock together

Shearing - cause masses of rock to slip

Convection Current

- heat comes up, cold goes down then heat up

Plates - broken enormous slabs from earth's crust and its rigid upper mantle; moves in different directions at different speeds, from 2-10 cm per year

Plate Boundary/Margins - place where two plates meet; has three types: convergent, divergent, transform boundary

1. Divergent Boundary

- tectonic plates move away from each other

- results in valley-like rift (also called dropped zone) where streams and rivers can flow into and narrow lakes are created

a. Continental-continental

*because of the opened crust, magma will replace and a new crust is created as magma cools and solidifies

*results in a rift then turns into rift valley as it gets wider then filled with water, turns to river and the like

*the other magma's that cant get out of the riff will then make a new opening which results to a volcano

b. Oceanic-oceanic (seafloor spreading)

- forms ocean ridges

- central rift - where seafloor spreading begins

- results to a Mid Ocean Ridge

- takes over millions of years

2. Convergent Boundary

- destructive plate boundary

- two tectonic plates move toward each other

*Subduction - one crust descends beneath the other and melts

*Subduction zone - place where subduction happens

a. Continental-Oceanic

- oceanic crust (denser) moves beneath the continental crust (lighter)

*parallel to the subduction zone continental volcanic arc (trenches) and series of volcanic eruptions are formed

*Trench - deep, narrow depression on the ocean floor caused by the collision and/or subduction of plates

b. oceanic-oceanic

*one that has become denser due to cooling (older plate) descends below another plate (younger plate)

*when the subducted crust partially melts, magma is produced and moves along the crack in the crust (other crust) to the top of the volcano above it: volcanic island arc (trenches)

*descending plate then reaches the mantle and melts

c. continental-continental

- folding of parts causing the formation of mountains (mountain range)

- parts of the continental crust descends to the other but not toward the mantle

- new continental crust ang angat because the old continental crust is more compact

3. Transform plate boundary

- plates slide past horizontally to each other

- crust is deformed/fractured

- no subduction, no subduction zone, therefore, no volcanoes but STRONG and LOTS of earthquakes

DRRM

Earthquake

- sudden release of energy from Earth's crust caused by movements along its enormous fractures

- natural vibration of the ground as a result of 2 blocks of Earth's crust sliding past each other

- often occurs in volcanic regions

Hypocenter/focus

- blocks that are gigantic fractures located beneath Earth's surface

- origin at which the earthquake occurs

Epicenter - the point directly above the focus on the surface

Faults - fractures or system of fractures caused by an earthquake

Fault line - long crack in the surface of Earth

Fault zone - complex system of fractures or deformations in the fault

Parts of a Fault:

1. Fault plane - flat surface that may appear vertical or sloping

2. Fault trace/scarp - the line it makes on Earth's surface

3.Hanging wall - upper side of fault plane

4. Footwall - lower side of fault plane

*There is no hanging wall/footwall when the fault plane is vertical

2 measurements that completely describe a fault plane:

1. Strike - direction of the fault trace on Earth’s surface

2. Dip - measurement of how steep the fault plane slopes

Types of Faults

Dip-slip faults - movement occurs along the dip direction; normal and reverse fault

1. Normal Fault - hanging wall drops; form under tension; rocks move apart/diverge

2. Reverse fault (thrust fault) - hanging wall moves up as a result of compression

3. Strike-slip fault- walls move sideways; usually vertical; lateral

Magnitude - amount of energy released during an earthquake; measured using a seismograph

Intensity - strength of ground shaking during an earthquake; amount of damage caused

Seismograph - instrument that detects and measures seismic waves

Seismometer

- internal part of seismograph

- works as a pendulum that swings back and forth, which is attached to a barrel that rotates and makes prints of the ground shaking

Seismogram - the recording a seismograph makes

Epicentral distance - the radius of the circle centered on the seismic station

Richter scale

- based the magnitude of earthquake from the size of the largest seismic waves generated by a factor of 10

- devised by Charles Richter

- most common scale for the magnitude of an earthquake

- sometimes called local magnitude

- a logarithmic scale of the wave amplitude of an earthquake

*Sample: Magnitude n is 10 times larger than magnitude n-1 (n minus 1 mwhaha)

*Magnitudes are based on a logarithmic scale (in base 10)

Modified Mercalli Intensity Scale

- assesses the strength of an earthquake based on the amount of damage to the structure

- invented by Giuseppe Mercalli (1902

- uses the observations of people who experienced the earthquake to estimate its intensity

- uses Roman numerals I-XII to designate the degree of intensity of the earthquake

- not scientific

- known as Rossi-Forel Intensity Scale before

Seismic waves - in the form of body waves and surface waves

- travel along and within the lithosphere

- causes the vibration that we feel during an earthquake

Different Types of Seismic waves

1. Body waves

a. Primary/Compressional waves (P-waves) - compress and pull rocks in a particular direction along which the waves are travelling; faster than S-waves

b. Secondary/Transverse waves (S-waves) - cause rocks to move at right angles, in relation to the direction of the wave.

2. Surface waves - moves in two directions as they pass through a rock

a. Love waves (L-waves) - sweep the surface in a side-to-side movement; its motion is transverse

b. Rayleigh waves (R-waves) - shake the ground in an up-and-down movement