Earth Materials and Processes: Endogenic Processes

Vocabulary and concepts regarding endogenic processes, magma formation, rock deformation, faults, and folds based on Earth Materials and Processes notes.

Endogenic Process

Processes that are formed or occurring beneath the surface of the Earth.

Magma

A mixture of molten rock, minerals, and gases, usually composed of a hot liquid base called the melt, crystallized minerals, solid rocks, and dissolved gases.

Asthenosphere

The upper portion of the mantle, located between $100\,km$ to $350\,km$ deep, where the temperature is high enough that most rock is melted.

Magma Temperature Range

Magma typically reaches temperatures between $600^{\circ}$ and $1340^{\circ}$ Celsius (noted in transcript as $600\,degree\,140\,degree$ Celsius).

Lava

Magma that emerges on the surface of the Earth, often appearing bubbly due to escaping gases.

Viscosity

The resistance to flow; in magma, it increases with higher silica content and decreases with increasing temperature.

Intrusion

A process where magma moves into a low-density area of another geologic form, such as sedimentary rock, and cools to become a pluton.

Pluton

An igneous intrusive rock developed when an intrusion of magma cools and hardens beneath the surface.

Magma Chamber

An area within the upper mantle and crust where magma collects and is layered by density, with least dense magma at the top and densest at the bottom.

Decompression Melting

A way to generate magma involving the upward movement of the mostly solid mantle (convection) to an area of lower pressure.

Transfer of Heat

A way to generate magma that occurs when hot, liquid rock intrudes into the Earth’s crust and transfers heat to the surrounding crust as it solidifies.

Flux Melting

The generation of magma caused by the addition of water or carbon dioxide to rocks, which affects the melting point of the rock.

Felsic Magma

Magma low in iron but high in potassium and sodium ($Na_2O + K_2O$) and silica, forming granite rocks and having high viscosity.

Intermediate Magma

Magma with high silica content and high viscosity commonly found in erupting volcanoes; it produces Andesite Rock.

Mafic Magma

Magma with relatively low silica content but high in iron and magnesium ($FeO$, $MgO$, $CaO$); it has low viscosity and is the most fluid magma type.

Ultramafic Magma

The hottest and fastest flowing magma type; it no longer forms today because the planet is too cool.

Stress

The force that creates deformation in the shape and/or volume of rocks, often resulting from the movement of lithospheric plates.

Lithostatic Stress

Equal pressure exerted on rock from all directions because of the weight of overlying rock, similar to hydrostatic stress in water.

Differential Stress

Unequal stress on rocks caused by tectonic forces, categorized into tensional, compressional, and shear stress.

Tensional Stress

A type of differential stress where rock is stretched or pulled apart, typically where crustal plates diverge.

Compressional Stress

A type of differential stress where rock is pressed, squeezed, or pushed together, typically where crustal plates collide.

Shear Stress

A type of differential stress resulting in slippage and translation as rock is pulled in opposite directions.

Strain

The ability of a rock material to handle stress depending on the elasticity of the rock.

Elastic Deformation

A reversible strain where rock changes shape in response to small stresses but returns to its original shape when the stress is removed.

Brittle Deformation (Fracture)

An irreversible strain occurring near the Earth's surface where rock breaks because differential stress exceeds the rock's yield strength.

Joints

Fractures in rocks that show little or no movement at all.

Faults

Extremely long and deep breaks or large cracks in rock resulting from continuous pulling and pushing.

Dip-slip Fault (Normal Fault)

A fault involving vertical movement where tectonic tensional forces stretch brittle rocks; the hanging wall moves downward relative to the footwall.

Hanging Wall

The block of rock lying on the top of the fault surface.

Footwall

The block of rock lying below the fault surface.

Strike-slip Fault

A fault where brittle rocks are sheared and movement is chiefly horizontal; examples include sinistral (left-lateral) and dextral (right-lateral).

Reverse (Thrust) Fault

A fault occurring when brittle rocks are pushed by compressional tectonic forces, causing the hanging wall to move upward relative to the footwall.

West Valley Fault

A dominant strike-slip fault in the Philippines extending from Dingalan, Aurora through Metro Manila to Tagaytay, believed to impact as 'THE BIG ONE'.

Folds

Structures formed when rocks deform in a ductile manner under high temperature and pressure at great depth, causing them to bend instead of fracture.

Monocline

The simplest type of fold where horizontal layers are bent upward so that the two limbs of the fold remain horizontal.

Syncline

A fold structure where rock layers are bent downward, and the two limbs dip inward toward the hinge.

Anticline

A fold structure where rock layers are bent upward, and the two limbs dip away from the hinge, often forming mountains or ridges.