Geological Structures

Joints are fractures in rock without displacement. They form due to tension, shear, or compressive stresses. Joints can be classified based on their orientation relative to bedding, their geometry, genesis, and dip. Systematic joints are parallel while nonsystematic joints have irregular distributions. Joints influence groundwater flow, construction, and are important in mining and resource exploration. They provide pathways for fluid migration and impact slope stability.

This document discusses various mechanisms of rock folding. It defines folding as the bending of rock strata due to compressional forces. There are several types of fold mechanisms including buckling, bending, flexure folding, flexural slip, flexural flow, passive flow, and kink folding. Each mechanism is influenced by factors like temperature, pressure, fluid properties, and the composition and texture of the rock. Buckling involves shortening of rock layers under lateral pressure. Bending involves applying force across layers to produce gentle folds. Flexural slip forms parallel concentric folds through buckling or bending with slip along layering.

This document defines and describes different types of unconformities in geology. It begins by defining an unconformity as a break or gap in the geological record representing a period of erosion or non-deposition. It then describes the major types of unconformities, including angular, disconformity, non-conformity, and local unconformities. Finally, it outlines several ways that unconformities provide significance, such as indicating time intervals missing from the geological record, structural discordances between rock layers, evidence of past topography, and signs of weathering at the contact surface.

This document provides an overview of fold classification and its elements. It begins with an introduction to folds and their historical development. It then describes the key elements of folds such as hinge points, limbs, and axial planes. The majority of the document focuses on various systems for classifying folds based on criteria like fold closure, symmetry, plunge of the axial plane, and interlimb angle. It discusses classifications proposed by Ramsay and Fluety. In conclusion, it provides a geometrical classification of folds based on dip isogons, axial plane thickness, and orthogonal thickness as defined by Ramsay.

A fabric describes the spatial and geometric relationships that make up a rock at the microscopic to centimeter scale. It includes planar structures like bedding and cleavage, as well as the preferred orientation of minerals. There are different types of fabric including linear fabric formed by elongate minerals, planar fabric formed by platy minerals, and random fabric with no orientation. Foliation specifically refers to any planar arrangement of minerals or structures in a rock. Foliation can be primary, forming during rock formation, or secondary, resulting from deformation. Common types of secondary foliation include cleavage, schistosity, and mylonitic foliation. Lineation describes a preferred linear orientation of features in a rock, often related to deformation processes like intersection of planar

This document discusses different types of faults, their classification, and characteristics. It begins by defining a fault and explaining their importance in geology. The main types of faults discussed are normal faults, thrust faults, strike-slip faults, and oblique faults. Criteria for identifying faults and the role of fluids in faulting are also summarized. Brittle faults occur in the upper crust and are characterized by fractures, while ductile faults at depth can form mylonite rocks. The document provides an overview of fault geometry and mechanics.

The document discusses the texture of igneous rocks. Texture refers to the size, shape, nature and arrangement of constituents in a rock. It is best studied through thin sections under a microscope. There are three main factors for describing texture: degree of crystallization, crystal/grain size, and fabric. Crystal size can range from microscopic to visible by the naked eye. Fabric considers crystal shapes, sizes, and their mutual relationships, which can be equigranular, inequigranular, intergrowths, directive patterns, or intergranular. Texture provides insights into the cooling and crystallization history of magma.

This powerpoint presentation gives some basic information regarding structural geology,folds,joints,faults etc.

Stream capture, also known as river capture or stream piracy, is the process where a river or stream redirects its flow and starts flowing into another river's drainage basin instead of continuing into its own basin. This can occur where two drainage basins are separated by an erosion-resistant divide that is breached by headward erosion of one of the streams. Once the divide is breached, the stream will capture the tributaries of the neighboring basin and divert its entire flow into the new course. Stream capture events can result in changes to drainage patterns over time.

Shear zones are zones of highly strained rock that form under brittle, ductile, or intermediate conditions. They record a history of deformation and can indicate the sense and amount of displacement. There are several types of shear zones defined by the dominant deformation mechanism (brittle, ductile, semibrittle, brittle-ductile). Determining the sense of shear is important and can be achieved through studying offset markers, foliation patterns, shear bands, inclusion shapes, and other indicators exposed in the shear zone.

This lecture includes the fold terminology and classification of folds based of different criteria. Classification of folds based on: Direction of closing Attitude of axial surface Size of interlimb angle Profile Ramsay Classification of folds

This document discusses different types of erosional and depositional landforms created by river processes. It describes landforms such as V-shaped valleys and waterfalls that are created by erosion, and floodplains and deltas that are formed by deposition. It also explains the factors that influence fluvial erosion and the formation of various erosional features like interlocking spurs, rapids, and potholes.

The document discusses different types of unconformities: - Angular unconformity occurs when rock layers above and below are not parallel due to erosion and deposition over a long period of time with changes in bedding orientation. - Nonconformity separates older crystalline rocks from overlying younger sedimentary or volcanic rocks, representing a long period of erosion. - Disconformity has parallel bedding above and below, separated by erosion over some time. - Local unconformity is similar to a disconformity but represents only a short period of non-deposition over a small area.

Anderson's theory of faulting predicts that the orientation of faults depends on the principal stresses. It assumes reverse faults dip at 30 degrees, normal faults dip at 60 degrees, and strike-slip faults are vertical. However, exceptions like low-angle normal faults exist. Pore fluid pressure or pre-existing weaknesses in the rock can allow faults to form at shallower angles. The rolling-hinge model also explains how low-angle normal faults can develop.

Joints are cracks or fractures in rocks that divide the rock mass into blocks. They form due to tensile and compressive stresses from processes like cooling/crystallization of igneous rocks, erosion, seismic activity, and tectonic plate movement. Joints can be systematic or non-systematic, and are classified by their orientation, geometry, and origin. Joints are important both geologically and economically, as they influence groundwater flow, quarrying, tunnel construction, and more.

This document summarizes igneous petrology and the structure and composition of the Earth's interior. It discusses how the Earth is composed of layers including the crust, mantle, outer core, and inner core. The crust is divided into oceanic and continental crust. The mantle makes up most of the Earth's volume and is composed of ultramafic rock. Heat transfer mechanisms like conduction, convection, and advection are described. The geothermal gradient and how temperature increases with depth is also summarized. Plate tectonics and mantle convection are driving the dynamic cooling of the Earth.

This document discusses sedimentary structures, which are macroscopic features formed during sediment deposition. It classifies sedimentary structures based on their morphology and formation processes. The key types discussed are physical structures like bedding, cross-bedding, and ripple marks formed directly by sedimentation. Chemical structures like nodules and concretions are formed by precipitation. Biogenic structures such as stromatolites and trace fossils provide evidence of ancient life. Studying sedimentary structures can provide insight into depositional environments, paleocurrents, and stratigraphic relationships.

The document provides information about folds and faults. It defines folds as bent or curved rock layers, and describes common fold types like anticlines and synclines. It also defines various fault types including normal faults, thrust faults, strike-slip faults, and oblique faults. Specific structures are described like the San Andreas Fault, which is a major strike-slip fault in California. Dip, strike, heave and throw are also defined in relation to describing the orientation and movement of geological structures.

what is a geologic structure? Plate Tectonics STRUCTURAL GEOLOGY & GEOTECTONICS Kinds of Folds Fold Classification Faults Dip-slip Faults

Geological structures- التراكيب الجيولوجيه Geological Structures What are Geologic Structures? إيه هيا التراكيب الجيولوجيه؟ Division of Structures تقسيم للتراكيب الجيولوجيه A- Primary structures  Ripple marks  Mud cracks  Cross bedding  Graded bedding  Burrows B- Secondary Structures  Folds  Faults  Joints  Unconformities What are Geologic Structures? إيه هيا التراكيب الجيولوجيه؟  Geologic structure is any feature in rocks that results from deformation, such as folds, joints, and faults. اى شكل فى الصخر ينتج من خلال عملية التشويه مثل : الصدوع والطيات هى التشققات والتصدعات الضخمة والالتواءات العنيفة التى تشوه صخور القشرة الارضية .  Geologic structures are usually the result of the powerful tectonic forces that occur within the earth. These forces fold and break rocks, form deep faults, and build mountains . Division of Structures • Primary (or sedimentary) structures: such as ripple marks, cross-bedding, and mud cracks form in sediments during or shortly after deposition. هى التراكيب الناتجة من تدخل العمليات الخارجية أثناء الترسيب • Secondary structures: is that structures formed after the formations of any kind of rocks, such as folds, faults, or unconformities. Primary structures They are any structures in sedimentary rock formed at or shortly after the time of deposition: such as: هى الاشكال التى تتخلف بالصخور تحت تأثير عوامل مناخية وبيئية خاصة مثل الجفاف والحرارة وتأثير الرياح والتيارات المائية وغيرها وبدون أى تدخل من جانب القوى والحركات الارضية أمثلة ذلك:  Ripple marks علامات النيم: هي تموجات رملية صغيرة تنشأ على سطح الطبقات الرسوبية بواسطة حركة الماء أو الهواء و تكون حروف علامات النيم متعامدة على اتجاه الحركة. They are wavelike (undulating) structures produced in granular sediment such as sand by unidirectional wind and water currents or by oscillating wave currents. Wind and current ripples. (Asymmetric Wave ripples. (Symmetric  Mud cracks التشققات فى الرواسب الطينية : حيث ينكمش سطح الرسوبيات الطينية مخلفة شقوقا مميزة فى فترات الجفاف Mud crack is a crack in clay-rich sediment that has dried out.  Cross bedding التطبق المتقاطع هو النمط الذي تسلكه الرسوبيات الجديدة المتراكمة عند تأثرها بأي من التيارات المائية أو الهوائية. عندما تستق

This document provides an overview of geological structures and the forces that cause them. It discusses stress, strain and rock strength, and how rocks deform through elastic, plastic and brittle mechanisms. The main types of stresses are described as tensional, compressional and shear. Geological structures include folds, fractures, joints and faults, which form through buckling or fracturing of rocks in response to these stresses. Specific fold types like anticlines and synclines are defined. Fractures include joints and faults, with joints involving no displacement and faults involving relative displacement of rock layers.

The document discusses the formation and types of mountains. It begins by explaining the general model of mountain formation, which involves accumulation of sediments, deformation and uplift during plate convergence, and isostatic rebound after erosion. It then describes the five main types of mountains: folded mountains from plate collisions, volcanic mountains from magma erupting, fault-block mountains from faults vertically displacing crustal blocks, erosion volcanic mountains formed by erosion, and dome mountains pushed up from underground magma. Finally, it compares characteristics of young, mature, and old mountains.

This document discusses different types of stresses that cause rock deformation, including confining stress, compression stress, tension stress, and shear stress. It also describes different types of resulting rock features such as folds, fractures, faults, and mountains. Specifically, it compares three types of folds - monoclines, anticlines, and synclines. It also differentiates between three main types of plate boundaries: divergent boundaries which cause tension stress and normal faults, convergent boundaries which cause compression stress and reverse faults, and transform boundaries which cause shear stress and strike-slip faults. Mountains can form at convergent plate boundaries through folding and faulting of rocks.

The document discusses unconformities, which are breaks or gaps in the geological record where one rock formation overlies another with evidence of erosion. There are three types of unconformities: parallel, angular, and nonconformity. Unconformities can be identified using structural features like angular relationships between tilted/folded rocks, sedimentary features like basal conglomerates, and paleontological features like changes in fossil assemblages. Precambrian unconformities can be difficult to identify due to deformation and metamorphism obscuring original relationships.

Structural geology deals with the geometry, distribution, and formation of rock structures within the Earth. Rocks can deform in either brittle or ductile manners depending on factors like temperature, pressure, strain rate, and composition. Brittle deformation results in fractures and faults while ductile deformation forms folds. Folds and faults provide evidence of past deformation events. Strike and dip are used to describe the orientation of planar geological features. Unconformities represent gaps in the geologic record due to periods of erosion or non-deposition between rock layers.

Structural geology is the study of rock structures and deformations within the Earth's crust. There are several types of rock structures that provide evidence of past deformation, including folds, faults, joints, and foliations. Folds occur when rock layers are bent, and there are different types such as anticlines, synclines, tight folds, overfolds, recumbent folds, and nappe folds. Understanding rock structures provides insight into the stress fields and tectonic processes that shaped the geological past.

Folds are bends in rock layers caused by forces within the Earth's crust. Folds can range in size from a few centimeters wide to several kilometers wide. Folds usually occur in series and resemble waves, with upward bends called anticlines and downward bends called synclines. Pressure from crustal movements deep in the Earth cause buried sedimentary rock layers to bend. Later erosion and uplift bring folded rock layers back to the surface. Folds helped form mountain systems like the Andes, Alps, and Himalayas.

The results of stress are folding and faulting. When a rock has stress put on it and does not break it is called folding. Folds appear as wave-like structures in rock layers. Some folds are small and can be seen in individual rocks and some folds are huge and can only be seen from the air.

This document defines key concepts in structural geology including stress, folds, and faults. It describes three main types of stress - tension, compression, and shear - and how they result in rock deformation. Folds form from compressional stresses and include anticlines, synclines, and monoclines. Faults are fractures in the crust where movement has occurred, and there are three main types - normal faults in areas of tension, reverse faults under compression, and strike-slip faults caused by shearing stresses.

Joints are fractures in rocks where there has been no displacement of the rock on either side of the fracture. There are two main types of joints - systematic joints which show regular patterns, and non-systematic joints which are irregular. Joints form through various processes including contraction during cooling, expansion and contraction from temperature changes, and tectonic stresses. Joints are important in geology as they influence rock strength and fluid flow underground.