A picture is worth a thousand words, but not all pictures are created equal. The pictures we usually feature on Learning Geology are field pictures showing Geological structures and features and many of them are high quality gem and mineral pictures. The purpose is to encourage students and professionals' activities by promoting "learning and scope" of Geology through our blogs. In the end of 2016, we are sharing with you the 10 best photos of 2016 which we have posted on our page. P.S: we always try our best to credit each and every photographer or website, but sometimes it’s impossible to track some of them. Please leave a comment if you know about the missing ones. 1. Folds from Basque France Image Credits: Yaqub ShahYaqub Shah 2. Horst and Graben Structure in Zanjan, Iran Image Credits: https://www.instagram.com/amazhda 3. A unique Normal Fault 4. The Rock Cycle The rock cycle illustrates the formation, alteration, destruction, and reformation of earth materials, and typically over long periods of geologic time. The rock cycle portrays the collective system of processes, and the resulting products that form, at or below the earth surface.The illustration below illustrates the rock cycle with the common names of rocks, minerals, and sediments associated with each group of earth materials: sediments, sedimentary rocks, metamorphic rocks, and igneous rocks. Image Credits: Phil Stoffer 5. An amazing Botryoidal specimen for Goethite lovers! Image Credits: Moha Mezane 6. Basalt outcrop of the Semail Ophiolite, Wadi Jizzi, Oman Image Credits: Christopher Spencer Christopher Spencer is founder of an amazing science outreach program named as Traveling Geologist. Visit his website to learn from him 7. Val Gardena Dolomites, Northern Italy 8. Beautiful fern fossil found in Potsville Formation from Pennsylvania. The ferns most commonly found are Alethopteris, Neuropteris, Pecopteris, and Sphenophyllum. Image Credits: Kurt Jaccoud 9. Snowball garnet in schist Syn-kinematic crystals in which “Snowball garnet” with highly rotated spiral Si. Porphyroblast is ~ 5 mm in diameter. From Yardley et al. (1990) Atlas of Metamorphic Rocks and their Textures. 10. Trilobite Specimen from Wheeler Formation, Utah The Wheeler Shale is of Cambrian age and is a world famous locality for prolific trilobite remains. Image Credits: Paleo Fossils
10 Amazing Geological Folds You Should See Folds are some of the most common geological phenomena you see in the world – a geolo...
A picture is worth a thousand words, but not all pictures are created equal. The pictures we usually feature on Learning Geology are field pictures showing Geological structures and features and many of them are high quality gem and mineral pictures. The purpose is to encourage students and professionals' activities by promoting "learning and scope" of Geology through our blogs. In the end of 2016, we are sharing with you the 10 best photos of 2016 which we have posted on our page. P.S: we always try our best to credit each and every photographer or website, but sometimes it’s impossible to track some of them. Please leave a comment if you know about the missing ones. 1. Folds from Basque France Image Credits: Yaqub ShahYaqub Shah 2. Horst and Graben Structure in Zanjan, Iran Image Credits: https://www.instagram.com/amazhda 3. A unique Normal Fault 4. The Rock Cycle The rock cycle illustrates the formation, alteration, destruction, and reformation of earth materials, and typically over long periods of geologic time. The rock cycle portrays the collective system of processes, and the resulting products that form, at or below the earth surface.The illustration below illustrates the rock cycle with the common names of rocks, minerals, and sediments associated with each group of earth materials: sediments, sedimentary rocks, metamorphic rocks, and igneous rocks. Image Credits: Phil Stoffer 5. An amazing Botryoidal specimen for Goethite lovers! Image Credits: Moha Mezane 6. Basalt outcrop of the Semail Ophiolite, Wadi Jizzi, Oman Image Credits: Christopher Spencer Christopher Spencer is founder of an amazing science outreach program named as Traveling Geologist. Visit his website to learn from him 7. Val Gardena Dolomites, Northern Italy 8. Beautiful fern fossil found in Potsville Formation from Pennsylvania. The ferns most commonly found are Alethopteris, Neuropteris, Pecopteris, and Sphenophyllum. Image Credits: Kurt Jaccoud 9. Snowball garnet in schist Syn-kinematic crystals in which “Snowball garnet” with highly rotated spiral Si. Porphyroblast is ~ 5 mm in diameter. From Yardley et al. (1990) Atlas of Metamorphic Rocks and their Textures. 10. Trilobite Specimen from Wheeler Formation, Utah The Wheeler Shale is of Cambrian age and is a world famous locality for prolific trilobite remains. Image Credits: Paleo Fossils
Folds is A wave-like geologic structure that forms when rocks deform, There are alot of types of folds, Check it out for more info and amazing photos
10 Amazing Geological Folds You Should See Folds are some of the most common geological phenomena you see in the world – a geolo...
Explore patrickkuhl's 1855 photos on Flickr!
Applying basic geologic principles: Laws of original horizontality, superposition, and cross-cutting relationships explain the or...
Pulau Banta island in the Banta Sea. Credit: Jialiang Gao/Wikimedia Geologists have for the first time seen and documented the Banda Det...
10 Amazing Geological Folds You Should See Folds are some of the most common geological phenomena you see in the world – a geolo...
Drainage pattern a pattern created by stream erosion over time that reveals characteristics of the kind of rocks and geologic structures ...
Growth Fault Growth Fault a fault in sedimentary rock that forms contemporaneously and continuously with deposition so that the throw in...
If you get a question wrong, you can still click on the other answers. This will open up hints and explanations (if available), which will provide additional
10 Amazing Geological Folds You Should See Folds are some of the most common geological phenomena you see in the world – a geolo...
Columnar basalt, with its mesmerizing arrays of tightly packed, polygonal columns, is a geological marvel. These columns, often hexagonal in...
Fault anatomy Faults drawn on seismic or geologic sections are usually portrayed as single lines of even thickness. In detail, however, faults are rarely simple surfaces or zones of constant thickness. In fact, most faults are complex structures consisting of a number of structural elements that may be hard to predict. Because of the variations in expression along, as well as between, faults, it is not easy to come up with a simple and general description of a fault. In most cases it makes sense to distinguish between the central fault core or slip surface and the surrounding volume of brittlely deformed wallrock known as the fault damage zone, as illustrated in Figure 8.10. Simplified anatomy of fault. The fault core can vary from a simple slip surface with a less than millimeter-thick cataclastic zone through a zone of several slip surfaces to an intensely sheared zone up to several meters wide where only remnants of the primary rock structures are preserved. In crystalline rocks, the fault core can consist of practically non-cohesive fault gouge, where clay minerals have formed at the expense of feldspar and other primary minerals. In other cases, hard and flinty cataclasites constitute the fault core, particularly for faults formed in the lower part of the brittle upper crust. Various types of breccias, cohesive or non-cohesive, are also found in fault cores. In extreme cases, friction causes crystalline rocks to melt locally and temporarily, creating a glassy fault rock known as pseudotachylyte. The classification of fault rocks is shown in heading below. In soft, sedimentary rocks, fault cores typically consist of non-cohesive smeared-out layers. In some cases, soft layers such as clay and silt may be smeared out to a continuous membrane which, if continuous in three dimensions, may greatly reduce the ability of fluids to cross the fault. In general, the thickness of the fault core shows a positive increase with fault throw, although variations are great even along a single fault within the same lithology. The damage zone is characterized by a density of brittle deformation structures that is higher than the background level. It envelops the fault core, which means that it is found in the tip zone as well as on each side of the core. Structures that are found in the damage zone include deformation bands, shear fractures, tensile fractures and stylolites, and Figure below shows an example of how such small-scale structures (deformation bands) only occur close to the fault core, in this case defining a footwall damage zone width of around 15 meters. Damage zone in the footwall to a normal fault with 150–200 m throw. The footwall damage zone is characterized by a frequency diagram with data collected along the profile line. A fault lens is seen in the upper part of the fault. Entrada Sandstone near Moab, Utah. The width of the damage zone can vary from layer to layer, but, as with the fault core, there is a positive correlation between fault displacement and damage zone thickness (Figure below a). Logarithmic diagrams such as shown in Figure below are widely used in fault analysis, and straight lines in such diagrams indicate a constant relation between the two plotted parameters. In particular, for data that plot along one of the straight lines in this figure, the ratio between fault displacement D and damage zone thickness DT is the same for any fault size, and the distance between adjacent lines in this figure represents one order of magnitude. Much of the data in Figure below a plot around or above the line D=DT, meaning that the fault displacement is close to or somewhat larger than the damage zone thickness, at least for faults with displacements up to 100 meters. We could use this diagram to estimate throw from damage zone width or vice versa, but the large spread of data (over two orders of magnitude) gives a highly significant uncertainty. A similar relationship exists between fault core thickness (CT) and fault displacement (Figure below b). This relationship is constrained by the straight lines D=1000CT and D-10CT, meaning that the fault core is statistically around 1/100 of the fault displacement for faults with displacements up to 100 meters. (a) Damage zone thickness (DT) (one side of the fault) plotted against displacement (D) for faults in siliciclastic sedimentary rocks. (b) Similar plot for fault core thickness (CT). Note logarithmic axes. Data from several sources. Layers are commonly deflected (folded) around faults, particularly in faulted sedimentary rocks. The classic term for this behavior is drag, which should be used as a purely descriptive or geometric term. The drag zone can be wider or narrower than the damage zone, and can be completely absent. The distinction between the damage zone and the drag zone is that drag is an expression of ductile fault-related strain, while the damage zone is by definition restricted to brittle deformation. They are both part of the total strain zone associated with faults. In general, soft rocks develop more drag than stiff rocks. Fault rocks When fault movements alter the original rock sufficiently it is turned into a brittle fault rock. There are several types of fault rocks, depending on lithology, confining pressure (depth), temperature, fluid pressure, kinematics etc. at the time of faulting. It is useful to distinguish between different types of fault rocks, and to separate them from mylonitic rocks formed in the plastic regime. Sibson (1977) suggested a classification based on his observation that brittle fault rocks are generally non-foliated, while mylonites are well foliated. He further made a distinction between cohesive and non-cohesive fault rocks. Further subclassification was done based on the relative amounts of large clasts and fine-grained matrix. Sibson’s classification is descriptive and works well if we also add that cataclastic fault rocks may show a foliation in some cases. Its relationship to microscopic deformation mechanism is also clear, since mylonites, which result from plastic deformation mechanisms, are clearly separated from cataclastic rocks in the lower part of the diagram. Fault breccia is an unconsolidated fault rock consisting of less than 30% matrix. If the matrix fragment ratio is higher, the rock is called a fault gouge. A fault gouge is thus a strongly ground down version of the original rock, but the term is sometimes also used for strongly reworked clay or shale in the core of faults in sedimentary sequences. These unconsolidated fault rocks form in the upper part of the brittle crust. They are conduits of fluid flow in non-porous rocks, but contribute to fault sealing in faulted porous rocks. Pseudotachylyte consists of dark glass or microcrystalline, dense material. It forms by localized melting of the wall rock during frictional sliding. Pseudotachylyte can show injection veins into the sidewall, chilled margins, inclusions of the host rock and glass structures. It typically occurs as mm- to cm-wide zones that make sharp boundaries with the host rock. Pseudotachylytes form in the upper part of the crust, but can form at large crustal depths in dry parts of the lower crust. Crush breccias are characterised by their large fragments. They all have less than 10% matrix and are cohesive and hard rocks. The fragments are glued together by cement (typically quartz or calcite) and/or by microfragments of mineral that have been crushed during faulting. Cataclasites are distinguished from crush breccias by their lower fragment–matrix ratio. The matrix consists of crushed and ground-down microfragments that form a cohesive and often flinty rock. It takes a certain temperature for the matrix to end up flinty, and most cataclasites are thought to form at 5km depth or more. Mylonites, which are not really fault rocks although loosely referred to as such by Sibson, are subdivided based on the amount of large, original grains and recrystallised matrix. Mylonites are well foliated and commonly also lineated and show abundant evidence of plastic deformation mechanisms rather than frictional sliding and grain crushing. They form at greater depths and temperatures than cataclasites and other fault rocks; above 300 C for quartz-rich rocks. The end-member of the mylonite series, blastomylonite, is a mylonite that has recrystallized after the deformation has ceased (postkinematic recrystallization). It therefore shows equant and strain-free grains of approximately equal size under the microscope, with the mylonitic foliation still preserved in hand samples. Credits: Haakon Fossen (Structural Geology)
Tectonics is an AGU journal publishing original research describing the evolution, structure, and deformation of Earth’s lithosphere across the range of geologic time.
Jointed basalt columns, as the most famous and most beautiful basalt formations, exists on many places on earth. These unusual columns are predominantly hexagonal in cross-section, but basalt polygons with three to twelve or more sides can be observed.
Transgression and regression are two important concepts in geology that describe how the shoreline of a body of water moves over time. Tran...
History buff on the hunt for a budget-friendly stone formation? Or simply curious? If the gift shop, fences and entry fees at Stonehenge leave you stone cold,…
When the compressional force applied under high confining pressure, rock beds tend to yield folding. Fording result in shorting and thickening of rock bed Terminology Anticline, Syncline, Limb, Axial plain, Axis of fold,Plunge of fold Types of fold Symmetrical fold - Two limbs dip in same angle but in opposite direction, axial plain is vertical and passing through crest and tough. Asymmetrical fold- limbs dip in unequal angle in opposite direction. Axial plane need not necessarily pass through crest and tough, and it is inclined. Overturned fold - asymmetrical fold with one lime turned past the vertical and both limbs dip in same direction. Recumbent fold - folding is so intense that both limbs become almost horizontal and axial plain too in horizontal. lower limb gets overturned. Isoclinal fold - folds with parallel limbs 1. Vertical Isoclinal fold 2. Inclined Isoclinal fold Nonplunging fold- syncline and anticline whose axis are horizontal Terminology Angle of plunge - the angle of inclination of axis from the horizontal Direction of plunge - the direction in which the axis is inclined nose - indicate the direction of plunge. In anticline, plunge is directed towards nose and in syncline it is directed away from nose. Plunging fold - if axis are inclined Outcrop of plunge Anticlinorium - these are the complex large folds in the form of syncline and anticline with sub-fold on there limbs. Open - limbs meet at bents at an obtuse angle and thickness remain unchanged. Closed fold - folding is so tight that incompetent strata flow plastically towards crest and tough due to minimum stress. It cause thinning at the flank and thickening at crests. Doom and Basin - when strata are subjected to folding in two direction at right angle, each anticline convert to doom and syncline to basin. Doom is up-fold where beds dip radially outward in all direction from centre and vise verse. Fan fold - upright fold with both limbs overturned. The bed within the anticline are much compressed below while they open out above. Crest and tough are generally rounded. Chevron fold - fold with straight or nearly straight limbs, their crest and tough become sharp and angular. Homocline - when bed dip with same angle and direction for few kilometer or more. Monocline - local warping in horizontal strata. Rock beds lying at two level separated by steep inclined limbs. It is form by vertical movement and generally found fault below monocline. Structural Terrace - local flattening in uniformly dipping bed. Drag fold - minor fold developed within the incompetent bed during the process of major folding.
Fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of perman...
Tilted Rock Layers Tilted rock layers: The sedimentary layers in this large roadcut near Denver, Colorado, USA can be clearly recogni...
10 Amazing Geological Folds You Should See Folds are some of the most common geological phenomena you see in the world – a geolo...
