SCIENCE 10 ALL TOPICS

Plate tectonic theory

Plate tectonic theory

It is a theory that states that the Earth’s solid outer crust, lithosphere, is separated into major or minor plates that move along the asthenosphere.

Lithosphere

solid outer crust of the Earth

Asthenosphere

molten upper portion of the mantle

Layers of the Earth

Crust - Solid, Oceanic and Continental

Mantle - Solid, Upper mantle, asthenosphere, lower mantle

Outer core - liquid

inner core - solid

The Pacific Ring of Fire

It is a zone within the Pacific Ocean that covers a collection of moving plate edges forming a ‘ring’ of volcanoes that cause earthquakes

Length of the Pacific ring of fire

40,000 kilometer horseshoe shaped basin

active volcano

volcanoes that erupted within the last 10,000 years

how many active volcanoes are in the philippines?

24, according to philvocs

potentially active volcanoes

volcanoes that do not have a historical record of eruption but are considered morphologically young

inactive volcano

no eruption for atleast 10,000 years and are not expected to erupt. its morphology was modified by weathering and erosion

volcanic activity

buoyant molten rock (magma) rises towards the surface and extrudes as lava during volcanic eruptions

earthquakes

occurs when rocks in the lithosphere rupture or move in order to release energy and stress (same)

Faults

breaks in earth’s crust where rocks move or slide past one another. it needs to be an apparent displacement

parts of an earthquake

fault plane , epicenter, hypocenter

fault plane

surface where the slip occurs

hypocenter (focus)

location below the surface where the earthquake occurs

epicenter

surface directly above the hypocenter. it is also where the greatest damage takes place

faults in the philippines

eastern part - east luzon trough, philippine trench

western region - manila trench, negros trench, sulu trench, cotabato trench

when did seismic activity in the philippines start getting recorderd

spanish colonization late 15th century. instrumentally derived parameters started 1892 and onward

measures in describing the strength of earthquakes

intensity and magnitude

intensity

measure of the degree of shaking experienced in an area (personal account)

magnitude

quantitative measurement relying on the data from seismic records along with other techniques (using machines n seismograph)

how to measure magnitude

seismograph

how to measure intensity

mercalli scale

what do mountain and mountain belts in the ph have and not have

in ph, mountain belts have tropical vegetation but no alpine peaks

most prominent mountain range in the philippines

central cordillera (cuts across the north of Luzon strait from the northern boundary to the central plain

highest mountain in luzon, 3rd highest in the archipelago

mt pulag (2,922m)

kitanglad mountain range

located on the northern central part of bukidnon. highest peak is mt dulang-dulang at 2,941m

major plates

north america, south america, pacific, african, eurasian, australian-indian, antarctic

boundary

something that indicates or fixes a limit or extent

divergent boundary / spreading centers / constructive margins

two plates move away from each other resulting in molten material rising and the formation of a new seafloor

ocean floor

landform formed due to divergent plate boundaries (ex. atlantic ocean)

convergent boundary / destructive margins

two plates move toward each other. it is where oceanic crust is destroyed and recycled. often associated with subduction zones where oceanic crust descends due to difference in density

three types of convergence

oceanic-continental (trench), oceanic-oceanic (volcanic island or island arc), continental-continental (mountain range)

movements of convergent boundaries

subduction and arcs

subduction

oceanic lithosphere is destroyed along trenches and is recycled back into the asthenosphere

arcs

long, sublinear chains of volcanoes following orientations of oceanic trenches

oceanic-oceanic convergence

when they converge, the older, denser plate sinks beneath the other. forms volcanic island arc or island arc

continental-continental convergence

it produces mountain ranges. they dont subuct they kinda just smash into each other cuz theyre both not that dense ykwim

oceanic-continental convergence

it forms trenches, and the oceanic crust subducts because it is denser than continental crust

transform plate boundaries / conservative margins

they slide past one another. no destruction or formation of the lithosphere

fault zones

areas where rocks are being broken and weakened by fault action

continental rifting

occurs within a continent and is caused by opposing tensional forces that stretch and thin the lithosphere

rift valley

lowland region that forms when the tectonic plates move apart. it can be found both in the land and ocean. they are created by the process of seafloor spreading

new ocean basins

it may form between two rifted continents once the lithosphere thins sufficiently for magma to erupt along an axis

Arthur Holmes

advocated the solid state flow model in the 1930’s. it can be compared to how hot water circulates in a kettle

ridge push

it is a force wherein hotter, less dense material forces itself up through a ridge.

slab pull

the pulling of the oceanic lithosphere downward at subduction zones. it is due to gravitational differences between the denser plate with its attached mantle and the lighter, overlying plate.

mantle drag

it moves molten material underneath the plates sidewards, but its effect is so small its considered negligible

hot spots

areas with abnormally high volcanic activity that have remained stationary for a very long time. since it does not move with the plates, a chain of volcanoes forms over those areas

mantle plumes

rising columns of hot rocks from the lower mantle that can cause melting as they reach the surface.

mantle convection

it is described as:

heating at the bottom caused by the heat loss from Earth’s core;

heating due to radioactive decay and;

cooling on the surface creating thick, cold lithospheric slabs denser than the mantle.

two models of mantle convection

“layer cake” model, and whole mantle convection

layer cake model

the mantle is divided into two zones of convection, the upper and lower mantle

whole mantle convection

where denser oceanic lithosphere sinks and may even reach the core-mantle boundary. the whole mantle is involved in the convection

gravity driven mechanisms of plate movement

slab pull and ridge push

solid state flow model

explains the convection cells in the mantle circulating heat causing plate motion

radioactivity in plate movement

it causes magma to ride where it expands to produce the plates above Earths surface

continental fit

hypothesized by Alfred Wegener, he observed that the continents fit each other well (notably Africa and South America), which suggests that they were once apart of a supercontinent before drifting apart

fossil evidence (continental drift theory)

specific deposits also provide evidence of similarities in conditions across continents. fossils of organisms, though similar, can be found in multiple continents

Paleomagnetic Data

refers to information obtained from studying the Earth's magnetic field recorded in rocks and sediments. It helps scientists understand the past movements of tectonic plates and the Earth's magnetic field over time.

curie point

specific temperature at which materials change or lose their magnetism

magnetic reversals

where the magnetic fields of Earth changes polarity (north to south, south to north)

three driving forces of plate movement

convection current, slab pull, ridge push

convection current / convection heat transfer

is a process that involves the movement of energy from one place to another

continental drift theory

states that the continents are slowly drifting round the Earth and was once a large landmass called Pangaea

Pangaea

a greek work meaning “All Earth”

seafloor spreading theory

proposed by american geophysicist Harry H. Hess in 1960, a geological process in which lithospheric crust split apart from each other

evidence from rock (continental drift theory)

similar matching rock formations found ocean apart

evidence from glaciation and ancient climates (continental drift theory)

Glacial striations can be found that match in Brazil and West Africa. Glacial deposits are also very similar in India, South America and in Vaal valley in SA

evidence from molten material (seafloor spreading theory)

scientists discovered rocks called pillow lavas along the mid-ocean ridges

evidence from magnetic stripes (seafloor spreading theory)

Rocks that make up the ocean floor lie in a magnetized stripes which hold a record of the reversals in the Earth’s magnetic field

evidence from drilling samples (seafloor spreading theory)

Rocks near ocean ridges are younger than the rocks farther from the ridge

evidences that supports continental drift theory

evidence from continental fit, evidence from fossils, evidence from rocks, evidence from coal beds and ancient climates, evidence from glaciation and ancient climates

evidences that suports seafloor spreading theory

evidence from molten material, evidence from magnetic stripes, evidence from drilling samples