Structural Geology

Plate Tectonics Theory

Unifying theory of geology

Plate Tectonics Theory

This theory says that lithosphere composed of segments (tectonic plates), plates in constant motion relative to one another

East African Rift System

A major continental rift zone in East Africa where the African Plate is splitting into the Nubian and Somali plates.

Baikal Rift Zone

An active continental rift in Siberia, Russia, characterized by deep seismicity and the formation of Lake Baikal.

Rio Grande Rift

A north-south trending continental rift in the southwestern USA, extending from Colorado to northern Mexico.

Red Sea Rift

A divergent boundary between the African and Arabian plates, leading to the formation of the Red Sea.

Afar Triple Junction

A tectonic meeting point of three rift systems in the Horn of Africa, actively spreading and forming new crust.

East Scotia Sea Rift

An active back-arc rift in the South Atlantic formed by subduction-related extension.

West Antarctic Rift System

A large, partially ice-covered rift system in Antarctica causing crustal thinning and volcanism.

Gulf of California Rift Zone

A young, active rift in northwestern Mexico where the Pacific Plate is diverging from the North American Plate.

North Fiji Basin Rift

A complex system of spreading centers and transform faults in the southwest Pacific Ocean.

Woodlark Rift

An active rift in Papua New Guinea marking the transition from continental rifting to seafloor spreading.

Sulu Sea Rift

A tectonic rift system within the Philippine Sea Plate, formed through intra-arc extension processes.

Pacific Plate

Which tectonic plate is the largest on Earth and is associated with the "Ring of Fire"?

North American Plate

The San Andreas Fault marks the boundary between the Pacific Plate and which major tectonic plate?

South American Plate

Which tectonic plate forms the eastern boundary of the Andes Mountains due to subduction of the Nazca Plate?

African Plate

The East African Rift System is a divergent boundary occurring within which major tectonic plate?

Eurasian Plate

The collision of the Indian Plate with which major plate resulted in the uplift of the Himalayas?

Antarctic Plate

Which tectonic plate covers the continent of Antarctica and is surrounded entirely by divergent boundaries?

Indo-Australian Plate

The plate responsible for the Himalayan orogeny is known as what tectonic plate?

Australian Plate

Which plate contains the continent of Australia and moves northeast, interacting with the Pacific Plate?

Nazca Plate

Which oceanic plate is subducting beneath the South American Plate, forming the Peru-Chile Trench?

Cocos Plate

Which small tectonic plate is subducting beneath Central America, contributing to volcanic activity in the region?

Philippine Mobile Belt

The subduction of the Philippine Sea Plate beneath the Eurasian Plate results in which tectonically active island arc?

Carribean Plate

The island of Hispaniola lies on the boundary of the North American Plate and which smaller tectonic plate?

Arabian Plate

The Red Sea Rift marks the divergent boundary between the African Plate and which tectonic plate?

Scotia Plate

Which small plate lies between the South American and Antarctic plates and is associated with complex transform boundaries?

Structural Geology

The scientific discipline that is concerned with rock deformation on both a large and a small scale

Deformation

Any process that affects the shape and size of a material

Translation

Which type of deformation involves a change in the position of a rock body without altering its orientation or shape?

Rotation

A rock unit that maintains its shape and size but changes its orientation due to tectonic forces has undergone what type of deformation?

Dilation

An increase or decrease in volume of a rock body without a change in shape or orientation is classified as what type of deformation?

Distortion

What type of deformation alters the shape of a rock body while keeping its volume relatively constant?

Rock Deformation

The movement of tectonic plates that creates stresses which cause rocks to deform

Strain

it is related to how the rock body reacts or responds to stresses that involves dilation and distortion

Linear Strain

What type of strain measures the change in length of a line such as elongation or compaction within a rock body due to deformation?

Shear Strain

What type of strain represents the change in angle between two originally perpendicular lines within a rock body?

Strain = (final length - original length) / original length

What is the formula of strain?

Stretch = final length / original length

What is the formula for stretch?

Pure Shear (Coaxial Strain)

What type of deformation involves homogeneous flattening or stretching without rotation of material lines, typically resulting from coaxial compression or extension?

Simple Shear (non-coaxial strain)

What type of shear deformation involves a change in shape with rotation of material lines, typically caused by differential motion along parallel planes?

Shear strain = change in x direction / height

What is the formula for shear strain

Stress = Force / Area

What is the formula for Stress?

Stress

What is the force applied per unit area within a rock that can cause deformation?

Normal Stress

What type of stress acts perpendicular to a given plane and can either compress or extend a rock body?

Tangential Stress

What type of stress acts parallel to a surface and contributes to the distortion of a rock body?

Shear Stress

What type of stress acts parallel to a surface and causes parts of a rock to slide past each other?

Elastic Deformation

What type of deformation is reversible, where a rock returns to its original shape once stress is removed which occurs at very low stresses environment?

Ductile or Plastic Deformation

What type of deformation results in permanent bending or flow of rocks under stress without fracturing which result to bending or fold of rock?

Brittle Deformation (Fracturing)

What type of deformation occurs when rocks break or crack in response to stress, typically at shallow crustal levels?

Brittle Material

Materials with low Temperature, low confining pressure, and high strain rate are?

Ductile Material

Materials with high temperature, high confining pressure, and low strain rate

Young’s Modulus

It describes the ability of a material to resist elastic deformation

Young’s Modulus

It is expressed as the ratio between stress and strain

Poisson’s Ratio

It is the ratio of transverse contraction or expansion strain to longitudinal extension strain in the direction of stretching force

Poison’s Ratio

It is expressed as the ratio between the transverse strain and the longitudinal strain

Bulk Modulus

It is the measure of incompressibility

Bulk Modulus

The ability of a substance to withstand changes in volume when being compressed

Bulk Modulus

It is expressed as the ratio between pressure and strain

Bedding

What is the most fundamental primary structure formed by the settling of sediment in layers?

Cross-Bedding

What inclined layering within a bed indicates deposition by wind or water currents?

Graded Bedding

Which structure shows a gradual decrease in grain size from bottom to top of a bed?

Ripple Marks

What small-scale ridges form on sediment surfaces due to flowing water or wind?

Mud Cracks

What feature forms polygonal cracks due to drying of wet sediments?

Raindrop impressions

What impressions are formed by raindrops impacting soft sediment surfaces?

Load Casts

What bulbous structures form when heavier sediment sinks into softer underlying layers?

Flute Casts

What erosional structures at the base of beds are used to determine flow direction?

Sole Marks

What sedimentary structures are found on the sole of beds and indicate stratigraphic top?

Concretions

What rounded bodies form from localized cementation within a sedimentary layer?

Interference ripples

What flat-topped ripple structures are formed by combined wave and current action?

Tool Marks

What are grooves or linear impressions formed by objects dragged along the seafloor?

Bouma Sequence

What structure indicates rapid sedimentation from turbidity currents?

Mud Lamination

What fine laminations in mudstone represent quiet water deposition?

Laminae

What term describes beds thinner than 1 cm in sedimentary rocks?

Bed

What term describes beds thicker than 1 cm in sedimentary rocks?

Normal Bedding

What graded bedding unit consists of sand at the bottom and mud at the top?

Rhythmic bedding

What type of bedding shows alternating layers of different grain sizes?

Lenticular bedding

What bedding type shows curved surfaces forming lenticular sand bodies?

Syneresis cracks

What structure forms by the filling of mud cracks with overlying sediments?

Symmetrical ripple marks

What sedimentary feature indicates wave oscillation near the shoreline?

pahoehoe

What structure forms from lava with wrinkled or ropy surfaces?

Aa lava

What blocky and jagged lava structure forms from more viscous lava flows?

Vesicles

What term describes gas bubble cavities preserved in volcanic rocks?

Amydales

What is the name for elongated vesicles due to flow in lava?

Biogenic Structures

What sedimentary structure forms from bioturbation by organisms?

Bioturbation

the disturbance and mixing of sediments or soil by living organisms.

Pillow Lava

What primary volcanic structure forms when lava cools rapidly under water?

Ash Fall Layers

What fine sediment structure forms from settling of ash in calm waters?

Stromatolites

What are sedimentary structures produced by microbial mats in carbonates?

Ooids

What are concentrically layered carbonate grains formed in high-energy settings?

Chicken-wire structure

What is the name of structures formed by desiccation of evaporite layers particularly gypsum and anhydrite?

Hopper crystals or Halite

What structure is formed by the growth of salt crystals in sediment?

Fossiliferous bedding

What structure consists of aligned fossil fragments in carbonate rocks?

Vesicular structures

What structure results from gas bubbles that do not escape magma?

Columnar Joints

What are planar fractures formed during the cooling of lava?

Chill margin

What feature indicates magma rapidly cooled down against cold rock margins?

Slump Structures

What structure indicates slumping or soft-sediment deformation?

Flame Structures

What deformation feature occurs due to differential loading on wet sediments?

Hummock cross-stratification

What feature results from wave reworking of soft sediments during storms?

Cross-bedding and flute casts

What sedimentary structures are used as paleocurrent indicators?