EARTHSCI FINALS COMPLETE

Pacific Ocean basin

largest, deepest, and oldest existing ocean basin. More trenches, and more frequent tsunamis happen here. It has been shaped by plate tectonics.

Four Major Ocean Basins

• North and South Pacific

• North and South Atlantic

• Indian

• Arctic

Continental shelf

Partly shallow extension of the continent underwater.

Continental slope

Transition zone of continental shelf and deep ocean floor. It starts from oceanic crust to continental crust.

Continental rise

It is where the ocean begins. All basaltic and oceanic rocks are found here. It is the place where the sediments from land are washed. The continental margin starts from continental shelf up to continental rise.

Abyssal plain

The flattest part of the ocean. 50 % of the earth’s surface is being covered by this plain.

Island

It’s not just a piece of land floating up in the middle of the sea, it is part of the ocean basin that extends up from the ocean floor.

Seamount

It is an undersea mountain. The erosion caused by waves destroyed the top of a seamount which caused it to be flattened.

Trench

It is the deepest part of the ocean.

Mid-oceanic ridge

The seafloor mountain system which is situated in the middle of the ocean basin. It is where upwelling of magma happens which causes the sea floor to spread.

Wilson Cycle

explains the process of the opening (beginning) and the closing (end) of an ocean which is driven by Plate Tectonics.

J. Tuzo Wilson

Canadian Geophysicist that the Wilson Cycle is named after

6 Stages of the Wilson Cycle

1. Embryonic Ocean Basin

2. Juvenile Ocean Basin

3. Mature Ocean Basin

4. Declining Ocean Basin

5. Terminal Ocean Basin

6. Suturing

Embryonic

• Motion: Uplift

• Complex system of linear rift valleys on continent

• e.g. East African Rift Valleys

Juvenile

• Motion: Divergence (Spreading)

• Narrow seas with matching coasts

• e.g. Red Sea

Mature

• Motion: Divergence (Spreading)

• Ocean basin with continental margins

• e.g. Atlantic and Arctic Oceans

Declining

• Motion: Convergent (Subduction)

• Islands arcs and trenches around basin edge

• e.g. Pacific Ocean

Terminal

• Motion: Convergent (Collision and Uplift)

• Narrow, irregular seas with young mountains

• e.g. Mediterranean Seas

Suturing

• Motion: Convergence and Uplift

• Young to mature mountain belts

• e.g. Himalayas Mountains

Metamorphism

is one of the geologic processes in which rocks change in form, composition, and structure due to intense heat and pressure and sometimes with the introduction of chemically active fluids.

Geothermal gradient

• The rate at which temperature increases with depth in the Earth’s crust

• varies on plate tectonic settings like the thickness of the crust or whether the area is in the subduction zone between oceanic and continental or under the converging two continental crusts.

Factors involved in metamorphism

• Temperature

• Pressure

high-pressure metamorphism

metamorphism in the subduction zone is characterized by

moderate-pressure metamorphism

the collision zone between two continental crusts is marked by

Vertical Stress

is the stress or pressure exerted on the rock by the weight of overlying material such as in burial metamorphism. This type of pressure is the same in all directions and makes the rocks to fracture or deform.

Differential Pressure

is imposed by a force in a particular direction

guides the shape and orientation of the new crystals formed as minerals recrystallize under the influence of both heat and pressure. This results in a textural change such that the minerals are elongated in the direction perpendicular to the directed stress and this contributes to the formation of foliation.

Foliation

is a set of flat or wavy parallel cleavage planes produced by deformation under directed pressures

Serpentinization

Metamorphism caused by hydrothermal fluids also occurs in mid-ocean ridges where hot lava, coming out of the fissures, reacts with mineral-rich ocean water. This causes serpentines to form through oxidation and hydration chemical reaction of peridotites- olivine-rich rocks at the base of the oceanic crust.

Regional Metamorphism

forms foliated metamorphic rocks such as Gneiss and Schist due to high temperature and pressure imposed on large parts of the crust.

Contact Metamorphism

which is prominent in areas where surrounding rocks are exposed to heat coming from magma intrusion within the layers of the rocks. Marble, quartzite, limestone, and other granoblastic rocks with large visible crystals of minerals may be formed through contact metamorphism.

Shock Metamorphism

which takes place when the heat and shock waves from meteor or asteroid impact transform rocks immediately around the impact site. Examples of this are the transformation of mineral graphite into ultra-high-pressure polymorph diamond and the conversion of quartz minerals into coesite under high shock pressures.

Burial Metamorphism

occurs at lower temperature and pressure which transforms sedimentary rocks that had undergone diagenesis into low-grade metamorphic rocks through relatively low temperature and pressure. Partial alteration of the mineralogy and texture may occur while other sedimentary structures are usually preserved.

Tensional stress

• type of stress

• causes rocks to be pulled apart that result to lengthening and break apart. This type of stress can be found at divergent plate boundaries.

Compressional stress

• type of stress

• causes rocks to fold or fracture. It squeezes rocks together. Compression is the most common type of stress in convergent plate boundaries.

Shear Stress

• type of stress

• happens when forces slide pass each other in opposite direction which results to slippage and translation. This is the most common stress found in transform plate boundaries

Faults

• rock under ample stress can crack, or fracture. The fracture is called a joint because there is a block of rock left standing on either side of a fracture line.

Footwall

• rock that is below the fault.

Normal faults

are the most common faults at divergent boundaries. In relation to the footwall, it develops as the hanging wall drops down.

East African Fault

example of a normal fault

Reverse faults

This type of fault is most common at the convergent boundaries. It forms when the hanging wall moves up.

Strike-slip faults

This type of faults formed when the walls move sideways. It can be either right lateral or left lateral. It is mostly common on transform plate boundaries

Himalayas and Rocky Mountains

Mountain ranges created by reverse faults

San Andreas Fault

example of a strike-slip fault

SONAR

a device that bounces sound waves off underwater objects and then record the echoes of these sound waves

Magnetometer

were attached to ships and allowed scientists discovered a lot about the magnetic properties of the seafloor.

Harry Hess

explained how the convection currents in the Earth’s interior make the seafloor spread.

Convection current

carry heat from the molten materials in the mantle and core towards the lithosphere. These current ensures that the “recycled” materials formed in the lithosphere were back to the mantle.

Molten materials, magnetic strip, drilling sample

Three evidence of seafloor spreading

Evidence from molten materials

• Evidence for seafloor spreading

• rocks shaped like pillows (rock pillows) show that molten materials have erupted again and again from cracks along the mid-ocean ridge and cooled quickly.

Evidence from magnetic strip

• Evidence for seafloor spreading

• rocks that make up the ocean floor lie in a pattern of magnetized stripes which hold a record of the reversals in magnetic field

Evidence from drilling sample

• Evidence for seafloor spreading

• core samples from the ocean floor show that older rocks are found farther from the ridge; youngest rocks are in the mid-ocean ridge

Hanging wall

rock that is placed on top of a fault

Weathering

the breaking down or alteration of rocks and minerals on Earth’s surface

Physical Weathering

the breaking down of rocks and minerals without changing its chemical composition

Frost Wedging

happens when water filling a crack freezes and expands, which in turn exerts pressure against the rock until it breaks

Salt Crystal Growth

happens when a salt in a solution precipitates in fractures of rocks which in turn exerts pressure to break it

Abrasion

happens when a rock or sediments bump into another rock causing its break down

Biological Activity

break down of rocks due to plant and animal activity

Exfoliation

breaking down of rocks that happens due to the reduction of pressures

Heat and Cold Cycles

breakdown of rock that happens due to its contraction and expansion after exposure to hot and cold cycles

Chemical Weathering

the breaking down of rocks and minerals caused by chemicals in rain or moving water

leads to rock’s change in chemical composition or weakening of its structure

Dissolution

happens when soluble minerals found in rocks are dissolved by water

Hydrolysis

breakdown of rock caused by its reaction with water

Oxidation

breakdown of rock by oxygen and water often giving iron rich rocks a rusty colored weathered surface

Factors Affecting Weathering

1. Properties of rocks

2. Climate

3. Soil and Vegetation

4. Length of Exposure

Primordial Heat

INTERNAL HEAT SOURCE

Earth was formed through accretion, where gravitational energy attracted gasses and dust from clouds, forming planetisimals. Heat was generated during this process, forming the earliest stage of Earth. Heat remained trapped in the core, causing convective and conductive transport to the mantle and surface, preserving some primordial heat.

Heat from the decay of radioactive elements

INTERNAL HEAT SOURCE

Earth's internal heat is primarily generated by radioactive decay, a process where naturally occurring isotopes decay, such as potassium-40, Uranium-235, Uranium-238, and Thorium-232. Other radioactive isotopes, though minor in production, contribute to the Earth's cooling process, despite their low heat capacity.

Dense core material

INTERNAL HEAT SOURCE

• Earth's inner core, composed primarily of iron and nickel, has a density between 12,600-13,000 kg/m3.

• Other heavy elements like gold, platinum, palladium, silver, and tungsten are also present in the core.

• The intense pressure in the inner core prevents the melting of iron and other elements, contributing to intense heat in the planet's interior.

Gravitational Pressure

INTERNAL HEAT SOURCE

• As one descends into Earth's interior, pressure increases due to the weight of overlying rocks.

• Near the center, pressure is 3 to 4 million times the pressure of the atmosphere at sea level.

• Rocks act as good insulators, reducing heat escape from Earth's surface.

• High temperatures cause beneath material to melt towards the central part of the earth, acquiring solid properties and possibly a plastic state.

Partial Melting

takes place because rocks are not pure materials. As temperature rises, some minerals melt and others remain solid. If the same conditions are maintained at any given temperature, the same mixture of solid and melted rock is maintained.

Decompression melting

takes place within Earth when a body of rock is held at approximately the same temperature but the pressure is reduced.

Flux melting

happens if a rock is close to its melting point and some water or carbon dioxide is added to the rock, the melting temperature is reduced and partial melting starts.

Intrusion

magma that moves up into a volcano without erupting. Like a balloon, this causes the volcano to grow on the inside.

Plutonism

refers to all sorts of igneous geological activities taking place below the Earth's surface

Plutonites

When the process of crystallization takes place inside the crust, the magmatic rocks produced

are igneous rock formations that are created when the process of crystallization and solidification of magma takes places below the Earth's surface and particularly in the crust

Extrusion

is an eruption of magmatic materials that causes land formation on the surface of the Earth.

Volcanism

is used to describe all geological phenomena that occurs on the natural terrestrial surface, such as the creation of volcanoes and hot springs.

It refers to all sorts of geological activities correlated with the flow and transportation of igneous material from the planet's interior towards the natural terrestrial surface.

Tectonic plate

is a massive, irregularly shaped slab of solid rock

Collision

motion of plates

wherein two continental plates are moved toward each other.

Subduction

motion of plates

when one plate subsides beneath the other plate.

Spreading

motion of plates

occurs when two plates are move away from each other

Transform faulting

motion of plates

occur when two plates slide past each other.

Convergent plate boundaries

occur when two plates collide, with subduction zones occurring when oceanic crust is subducted underneath. This results in island arcs, oceanic trenches, and back-arc basins. When oceanic crust meets continental crust, the denser oceanic plate subducts, creating mountain ranges like the Andes. Continental crust collides with another to create large mountain ranges.