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Mysteries of the earth!

The Ridge by River Clyde

Anticline followed by an Esker

This ridge is an anticline but what makes it different from an esker?

Esker

An esker is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several miles in length and, because of their peculiar uniform shape, somewhat resemble railroad embankments.

Geology

Most eskers are believed to form in ice-walled tunnels by streams, which flowed within and under glaciers. After the retaining ice walls melt away, stream deposits remain as long winding ridges. Eskers may also form above glaciers by accumulation of sediment in supraglacial channels, in crevasses, in linear zones between stagnant blocks, or in narrow embayment at glacier margins. Eskers form near the terminal zone of glaciers, where the ice is not moving as fast and is relatively thin (Easterbrook, 1999).The rate of plastic flow and melting of the basal ice determines the size and shape of the subglacial tunnel. This in turn determines the shape, composition and structure of an esker. Eskers may exist as a single channel, or may be part of a branching system with tributary eskers. They are not often found as continuous ridges, but have gaps that separate the winding segments. The ridge crests of eskers are not usually level for very long, and are generally knobby. Eskers may be broad-crested or sharp-crested with steep sides (Easterbrook, 1999). They can reach hundreds of kilometres in length.The concentration of rock debris in the ice and the rate at which sediment is delivered to the tunnel by melting and from upstream transport determines the amount of sediment in an esker. The sediment generally consists of coarse-grained, water-laid sand and gravel, although gravely loam may be found where the rock debris is rich in clay. This sediment is stratified and sorted, and usually consists of pebble/cobble-sized material with occasional boulders. Bedding may be irregular but is almost always present, and cross bedding is common (Easterbrook, 1999). Please look at the adjacent photo, and see the loose material that eskers are made of.
They are generally small to medium tills (sand to small rocks).

Etymology

The name esker is derived from the Irish word eiscir (Old Irish: escir), which means: "a ridge or elevation, especially one separating two plains or depressed surfaces" (Dictionary of the Irish Language). The term was used particularly to describe long, sinuous ridges, which are now known to be deposits of fluvio-glacial material. The best-known example of such an eiscir is the Eiscir Riada, which runs virtually the entire width of the island of Ireland from Dublin to Galway, a distance of about 100 miles, and is still closely followed by the main road linking those two cities.

References
Quin, E. G. (gen. ed.) (1983). Dictionary of the Irish Language. Dublin: Royal Irish Academy, 281. ISBN 0 901714 29 1. Easterbrook, D.J. (1999). Surface Processes and Landforms. New Jersey: Prentice Hall, 352. ISBN 0 13 860958 6. Trenhaile, Alan (2007). Geomorphology: A Canadian Perspective. Don Mills, Ontario: Oxford University Press, 188-191. ISBN 0-19-542474-3.

Anticline

In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships (i.e. younging direction) between various strata are unknown, the term antiform must be used.On a geologic map, anticlines are usually recognized by a sequence of rock layers that are progressively older toward the centre of the fold because the uplifted core of the fold is preferentially eroded to a deeper stratigraphic level relative to the topographically lower flanks. The strata dip away from the centre, or crest, of the fold.If an anticline plunges (i.e., is inclined to the earth's surface), the surface strata will form Vs that point in the direction of plunge. Anticlines are typically flanked by synclines although faulting can complicate and obscure the relationship between the two. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building.

Anticline terminology

Any fold whose form is convex upward is an antiform. Antiforms containing progressively younger rocks from their core outwards are anticlines.An anticline or antiform has a crest, which is the highest point on a given stratum along the top of the fold. A hinge in an anticline is the locus of maximum curvature or bending in a given stratum in the fold. An axis is an imaginary line connecting the hinges in the different strata in a two-dimensional cross-section through the anticline. Connecting the hinges or points of maximum curvature in the different layers in three dimensions produces an axial plane or axial surface. In a symmetrical anticline, a surface trace of the axial plane coincides with the crest. With an asymmetrical anticline, the surface trace of the axial plane or axis will be offset from the crest toward the steeper flank of the fold. An overturned anticline is an asymmetrical anticline with a flank or limb that has been tilted beyond perpendicular so that the beds in that limb are upside-down.A structure that plunges in all directions to form a circular or elongate structure is a dome. Domes are generally formed from one main deformation event, or via diapirism from underlying magmatic intrusions or movement of upwardly mobile, mechanically ductile, material such as rock salt (salt dome) and shale (shale diapir).An anticline, which plunges at both ends, is termed a doubly plunging anticline, and may be formed from multiple deformations, or superposition of two sets of folds, or be related to the geometry of the underlying detachment fault and the varying amount of displacement along the surface of that detachment fault. The highest point on a doubly plunging anticline (or any geologic structure for that matter) is called the "culmination."An elongate dome, which developed as the sediments were being deposited, is referred to as a pericline.

Economic significance

Structural trap: anticlinal fold Doubly-plunging or faulted anticlines, culminations, and structural domes are favoured locations for oil and natural gas drilling; the low density of petroleum causes it to buoyantly migrate upward to the highest parts of the fold, until stopped by a low-permeability barrier such as an impermeable stratum or fault zone. Examples of low-permeability seals that contain the hydrocarbons, oil and gas, in the ground include shale, limestone, sandstone, and even salt domes. The actual type of stratum does not matter as long as it has low-permeability. Periclines are important focal points for pooling of hot, metal-laden formational brines, which can form manto ore deposits, Irish-type lead-zinc deposits and uranium deposits, amongst others.ReferencesBates, Robert L., and Julia A. Jackson, editors. Dictionary of Geological Terms: Prepared under the direction of the American Geological Institute, Anchor Press/Doubleday, Garden City, New York. Davis, George H., Reynolds, Stephen J., 1996. Structural Geology of Rocks and Regions: John Wiley & Sons, Inc., New York. ISBN 0-471-52621-5Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution. 2nd ed. Belmont: Wadsworth Publishing Company, 1997. ISBN 0-314-09577-2The above is from Wikipedia, the free encyclopaedia

Where do you find oil and natural gas underground?

A wildcat exploration effort, which is what you are doing when you drill into an area that has not yet been explored for oil, can be helped by 140 years of geologic experience with finding oil.Organic material produced by death of plants and animals is commonly recycled by microbes and used as nutrients by other plants and animals. In some environments, microbial activity is suppressed, most commonly by shortage of oxygen. Anoxic or oxygen deprived environments are found in places like swamps, on the bottoms of stagnant lakes, or in parts of the deep ocean. Here organic material is deposited and buried with the sediment, forming a source rock. The source rock may be small or very extensive. An example of a source rock is the Albert oil shale located south of Moncton, NB.As buried organic material ages over geologic time, it is chemically modified. Sediments that are buried are heated by energy from the Earth. In the right conditions of temperature over time, known as the oil window, organic material will form oil and natural gas. If the sediments are too young or cool, the organic material is trapped in solid form as bitumen. If the temperature goes too high, oil will be chemically modified to form gasses, initially methane and later carbon dioxide.Formation of oil in the oil window creates a unique condition because liquid, the oil along with the water that is in most rocks, can move underground. Rocks contain microscopic holes, called pores, between the rock grains.

The liquid oil will move into the pores. If the pores in the rock are interconnected, the rock is said to be permeable. Permeable rocks are formed where many of the pores touch each other, like they do in sandstone or a conglomerate. Fractures through the rock can also improve the permeability be connecting many pores. Rocks like limestone, salt or dolostone have different permeability depending on the rock history; they can be permeable or have permeability enhanced by fracturing.Movement of oil from the source rock to areas where it is concentrated and can be removed quickly (on a human time scale) is what is needed to "strike it rich" with an oil well. Anticlines with the correct constituents in their layers are a great local to search for oil and natural gas. Using data from borehole samples gives researchers a good idea where to find oil and natural gas reservoirs.

Nova Scotia High Precision Network

Coordinate Referencing System - High Precision Network Also at the site there is a stake with an orange can attached, this is a marker for the Nova Scotia High Precision Network (NSHPN). The emergence of the use of the Global Positioning System (GPS) technology in surveying during the late 1980's and early 1990's was indicating that the existing control networks would not support the accuracy levels attainable with GPS. Another issue was the fact that GPS is based on a different datum than the ATS77 datum in use in the Maritimes. In 1992 the Maritime provinces commissioned a control survey task force report, which was prepared by the consultants Angus Hamilton and James Doig. The report was completed in March 1993 and two of the recommendations were: Design a new GPS based reference framework tied to Geodetic Survey Division’s (GSD) High Precision Network.

Establish and maintain a regional High Precision Network

In 1994, the Maritime provinces acted on these recommendations by cooperating in a joint GPS campaign with the federal government to establish the networks. The GSD high precision network became known as the Canadian Base Network (CBN), with nominal spacing of 200 km and the regional high precision network as the Maritime High Precision Network (HPN), with nominal spacing of 70 km. Each province also decided to further densify the Maritime HPN in their jurisdiction to a nominal spacing of 20 - 40 km. This would make it more accessible to GPS users. This new, highly precise GPS observed control network in the Nova Scotia portion became known as the Nova Scotia High Precision Network (NSHPN). It is comprised of the four CBN points and fourteen Maritime HPN points established in Nova Scotia in 1994 and the additional Nova Scotia densification points. In all there will be approximately 150 points in the NSHPN. Most of the stations are from the existing Nova Scotia Coordinate Control System (NSCCS) network.The NSHPN is integrated into the Canadian Spatial Reference System (CSRS) via its connection to the CBN and thus to the Canadian Active Control System (CACS). The CACS is the main source for precise GPS products in Canada.The last major GPS observation campaign was completed in the fall of 1998.

It is anticipated that the GPS processing and adjustment phases for the NSHPN project will be completed in 2000 with the adopted coordinates for the NSHPN points available by the summer of 2000. Preliminary coordinates are currently available for users. Them preliminary coordinates are most likely subject to changes at the 1-10 cm level.