PDF | Geology is the applied discipline of science and is now established as an interdisciplinary subject within engineering, earth and. Basic Geologic Principles: Minerals & Rocks. Mineral: . Indeed, plate tectonics is a fundamental component of Earth's rock cycle and controls the diversity. Library of Congress Cataloging-in-Publication Data Gill, Robin, – Chemical fundamentals of geology and environmental geoscience/Robin Gill.
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Physical Geology is a vast subject and it is not possible to cover all aspects in one book. This book Fundamentals of Physical Geology Download book PDF. Geology is the multi-disciplinary science that studies the earth and its history. .. The fundamental goal of the Department of Geology at Appalachian is to. What Is Geology? 2. Why Study Earth? 4. What Do Geologists Do? 6. Minerals and Rocks. 7. Fundamentals of Plate.
All joints are structural weaknesses, whose density, extent and orientation are major influences on rock mass strength section Massive rocks are those that have less fractures, joints or structural weaknesses of any kind.
Fault types are recognized by relationship of downthrow to dip of the fault plane. Fault gouge: finely ground rock paste within a thin zone along a fault plane. Fault drag: disturbance and folding of rock near a fault. Slickensides: scratches and polishing on fault planes, and on bedding plane faults within tight folds.
Veins: sheets of mineral infill deposited by hydrothermal water in fractures or fissures in rock. They occur in joints or faults. Most veins are of quartz or calcite — white streaks in rock faces. Larger veins mostly on faults can contain valuable minerals — may have been mined out. Faults commonly create zones of badly broken ground — that are weaker and less stable than the adjacent rock — with implications for foundation bearing capacity, slope stability and tunnel roof integrity.
Sudden movements along faults when tectonic stresses accumulate to overcome frictional resistance cause earthquakes — vibrations transmitted through the surrounding ground section Old faults including all those in Britain cannot displace ground surface that has evolved subsequent to any fault movement.
Fault line scarps and valleys may appear in a landscape due to differential erosion across the fault zone and adjacent contrasting rocks. Succession of rocks Older rocks generally lie below younger rocks, and are only exposed by erosion. Reference to old and young rocks by age avoids any confusion with high and low outcrops that refer only to their topographical positions.
Overfolds and recumbent folds have dips past vertical. Isoclines have parallel dips on both sides. Nappes are recumbent folds sheared along the central line with the development of a thrust fault, usually with large displacement.
Inlier is an outcrop of old rocks surrounded by the outcrops of younger rocks; its presence on a map indicates either an eroded anticline or a valley. Outlier is an outcrop of young rocks surrounded by old, due to either an eroded syncline or a hill. Unconformity is the plane or break between two sequences of rocks with different dips.
It indicates a period of earth movements and tectonic deformation between the times of sediment deposition. It forms a major structural break — the older rocks must be more lithified and folded, and perhaps more metamorphosed, than the younger rocks above the unconformity.
Escarpments, or cuestas, are asymmetrical hills of dipping beds of strong rock, exposed by differential erosion of weaker rocks above and below.
Unloading joints: stress-relief fractures close to and parallel to ground surface due to erosional removal of overburden cover rocks.
Landslip fissures: open fissure and normal faults developed in head zones of slopes prior to failure. Contraction joints: cooling joints in igneous rocks, including columnar basalt. Localized structures formed in shallow rocks and soils, by erosion processes and shallow ground deformation, unrelated to regional tectonic structures. Camber folds develop in level or low-dip rocks where a clay or soft shale underlies a strong sandstone or limestone.
The clay is plastically squeezed out from beneath the hill due to the differential loads upon it. Valley bulge is the floor lift since eroded away and the structural disturbance left beneath it. Most clay is squeezed out from close to the valley side or scarp edge , so that overlying stronger rocks sag and camber towards the valley.
Gulls are open or soil-filled fissures in the strong rocks of cambered valley sides, opened by camber rotation and perhaps also by sliding. Post-glacial cambered ground, or foundered strata, is common in the sedimentary rocks of England; it causes fissured rock masses and potential landslides along many valley sides and scarp faces.
Shapes of outcrops depend on the shape of the surface and the shape of the rock structure. Surface shape is known from topographic contours : therefore rock structure can be interpreted.
An important rule: where more than one interpretation is possible, the simplest is usually correct. Map interpretation is therefore logical and straightforward if approached systematically.
Maps remain the best way of depicting 3-D rock structure on a piece of paper. Six basic concepts cover all outcrop patterns, and enable most geological maps to be interpreted successfully.
Horizontal beds have outcrops that follow the contours because they are at constant altitude limestone on the Scar Hill map. Vertical beds have straight outcrops that ignore the contours the dyke on the Tan Vale map. Dipping beds have curved outcrops that cut across, and respond to, the contours — because outcrops shift downdip as erosion lowers the surface sandstone on both maps.
Dip direction is recognized by the V in Valley Rule: an outcrop of a dipping rock bends round a V shape where it crosses a valley, and the V of the outcrop points like an arrowhead in the direction of dip, regardless of the direction of valley slope and drainage. This works because the outcrop is shifted furthest downdip at its lowest point, where it crosses the valley floor as on the Tan Vale map and diagram. The rule does not apply in areas of low dip, where outcrops nearly follow contours, so point upstream.
On level ground, dipping beds have straight outcrops along the direction of strike. Succession is recognized by younger rocks coming to outcrop in direction of dip. Conversely, if succession is known, the dip is in the direction of younger outcrops — the easiest way to recognize dip on most maps. Width of outcrop is greater at lower dips — and on thicker beds.
The north-south section is drawn along the strike, so does not demonstrate the dipping geological structure. Unconformity is recognized where one outcrop of a younger bed cuts across the ends of outcrops of older beds as does the limestone on the Scar Hill map.
Faults are usually marked and keyed on maps. They may cut out, offset or repeat outcrops of beds. Fault dip is recognized by V in Valley Rule. Downthrow side of a fault is the side with younger outcrop because the older rocks have been downthrown to beneath surface level. Identify faults and unconformities structural breaks. Identify dips by the V in Valley Rule. Determine succession unless already given.
Identify fold axes from dips and outcrop bends. Draw stratum contours if detail is required. Draw cross-section to show sub-surface structure. Folds are recognized by changes in dip direction, and also by outliers and inliers not due to topography. Most important, folds are recognized by bends in outcrop: any outcrop bend must be due to either a fold or a topographic ridge or valley. Each outcrop bend should be interpreted as on the Scar Hill map. The topography and each geological boundary are constructed individually from the relevant contours, whose intersections on the section line are projected to their correct altitudes on the profile.
Three stages in drawing a cross-section through the geology on the Scar Hill map are shown below. The purple projection lines, and the large rings around their end points, are only included to demonstrate the construction of stages 1 and 2. Interpretation of the Scar Hill map Bends in outcrop are used to identify: 1. They are like topographic contours, except that they show the shape of buried geological structures.
Each contour is labelled with its altitude and the bed boundary to which it refers. They are drawn by joining points of known equal height on one geological boundary — where its outcrop crosses a topographic contour. The surface information of the map is therefore used to construct the stratum contours, which provide data on the underground geology.
With uniform dip, stratum contours are straight, parallel and equidistant. Stratum contours have been drawn below on part of the Tan Vale map. Depths to any rock can be read off at any point. The stratum contours indicate that a borehole drilled at point A would pass through 20 m of clay, and then reach the sandstone, which would continue to a depth of 30 m, below which lies the mudstone. Low relief cannot be shown accurately at these scales, and therefore stratum contours cannot be drawn to show the geology.
Principles of outcrop shape, bed relationships and structure recognition from section 07 still apply, but the interpretation and section drawing cannot rely on stratum contours. These are in parallel beds of roughly constant thickness. They are folded and crumpled into parallel curves.
Bed thinning and splitting is rarely seen in small areas. Beds do not form patternless wedges and blocks. Heavily faulted areas can provide local complexity.
Intrusions and volcanic rocks have more varied shapes. Drift sediments form thin, but variable, surface layers. Geological Map of Oakunder This is an example of a typical geological map: it shows all rock outcrops, and has some dip arrows to show structure; its stratigraphic column shows the succession and bed thicknesses; simplified topography only shows river valleys.
All maps should have a bar scale, which retains integrity when copied to different sizes. Add interpretation data to map. Find dips from V in Valley rule.
Find dips from succession rule. Outcrop widths indicate dip.
Three shale beds are distinguished: numbered in stratigraphic column, and labelled on map. Fault and dyke are both straight, so they are vertical.
Fault is minor — dies out to north, has small outcrop displacements. Bed sequences are mirrored across the axes of each fold. Assume locally uniform dip to draw stratum contours.
Along lines drawn between any pair of boreholes, distribute uniformly altitudes of the selected boundary or bed. Lines joining these interpreted points of equal altitude are therefore stratum contours.
With three boreholes, can only interpret and draw straight stratum contours. With more than three boreholes, can draw curved and converging stratum contours to show folding and nonuniform dips. Reliability depends on borehole spacing in relation to structural complexity.
Useful for initial interpretation of site investigation data. Applicable to any rock or drift layer, rockhead or fault. Ground profile is given or is drawn from topographic map. Outcrops are projected onto ground surface as in section Dips are obtained by using the given bed thicknesses as on right.
Fault can be ignored at first, because it is interpreted as minor. Oakunder Grit is drawn across both folds, linking the three outcrops. Fault is added so that base of Belvoir Grit does not have an outcrop.
Chapter 1 Introduction to Geology 1. Chapter 22 Summary Glossary About the Author Appendix 1 List of Geologically Important elements and the Periodic Table Appendix 2 Answers to Review Questions Appendix 3 Answers to Exercises Versioning History Book Information Book Description Physical Geology is a comprehensive introductory text on the physical aspects of geology, including rocks and minerals, plate tectonics, earthquakes, volcanoes, glaciation, groundwater, streams, coasts, mass wasting, climate change, planetary geology and much more.
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