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55-566: Forming the Atlantic segment of the boundary between the African and Eurasian plates, the AGFZ is largely dominated by compressional forces between these converging (3.8 to 5.6 mm/a (0.15 to 0.22 in/year)) plates, but it is subject to a dynamic tectonic regime that also involves extension and transform faulting . The oceanic lithosphere in the area is directly related to the opening of

110-471: A bond trader on Wall Street and in the U.S. Government bond market in Washington, D.C. She was life partner to the popular Classicist Edith Hamilton and together they raised the elder Reids' first grandchild, Francis Dorian Fielding. Reid's sister Ellen married the celebrated poet and preacher Henry van Dyke, who was the author of dozens of books, taught English at Princeton and served as U.S. Minister to

165-422: A career in research and teaching at Johns Hopkins. The Geology Department had been founded several years before and was then under the chairmanship of Charles Bullock Clark. Reid's relationship with other members of his department is uncertain, and his professional identity was fluid as well. Geophysics was a new field at that time, and Reid could later fairly claim to be the first American scientist to practice it as

220-541: A constant length, or decrease in length. These length changes are dependent on which type of fault or tectonic structure connect with the transform fault. Wilson described six types of transform faults: Growing length: In situations where a transform fault links a spreading center and the upper block of a subduction zone or where two upper blocks of subduction zones are linked, the transform fault itself will grow in length. [REDACTED] [REDACTED] Constant length: In other cases, transform faults will remain at

275-474: A constant length. This steadiness can be attributed to many different causes. In the case of ridge-to-ridge transforms, the constancy is caused by the continuous growth by both ridges outward, canceling any change in length. The opposite occurs when a ridge linked to a subducting plate, where all the lithosphere (new seafloor) being created by the ridge is subducted, or swallowed up, by the subduction zone. Finally, when two upper subduction plates are linked there

330-588: A geologist and was an elder brother of the celebrated neurosurgeon Harvey Cushing. Harvey Cushing went to Baltimore in 1896 to train at the newly founded Johns Hopkins Hospital before being chosen to head the surgery department at Brigham in Boston. Reid's trip to Alaska resulted in his first professional publication, a long article in volume IV of the National Geographic Magazine , in those years still an academic journal. During 1892 he made

385-564: A gymnast when young and an active mountain climber through much of his long life. He is not known to have produced any Ph.D. geophysicists through the geology department at Johns Hopkins, but he did serve as an advisor to students in other fields. Reid's son Francis Fielding earned an M.D. degree from the University of Maryland in 1930 but apparently did not practice medicine other than during his U.S. Army career. His daughter Doris Fielding eventually gave up pursuit of music and art to work as

440-551: A junction with another fault. Finally, transform faults form a tectonic plate boundary, while transcurrent faults do not. Faults in general are focused areas of deformation or strain , which are the response of built-up stresses in the form of compression , tension, or shear stress in rock at the surface or deep in the Earth's subsurface. Transform faults specifically accommodate lateral strain by transferring displacement between mid-ocean ridges or subduction zones. They also act as

495-465: A second expedition (like the first, evidently self-financed) with a small crew of hired men. Why any of the students and others from his first trip did not come a second time is unknown. Conditions in Alaska during that era could be at best called “pioneer,” and field scientists had no choice but to live in huts on the ice or else on camp on bare rock. The U.S. Navy sent a vessel past once each week during

550-465: A significant private income, at least some of which he dedicated to scientific research. He was later memorialized by colleague Andrew Lawson as having been “blessed with a charming character,” that it was “always a joy to meet him.” Lawson also remarked that Reid might seem “austere” to those unknown to him, yet that was typical for the Southern elite of his day. He was a small but physically strong man,

605-519: A specialty. By 1911, and after a series of promotions, he was granted the title Professor of Dynamic Geology and Geography. In 1902, Reid began to collect seismological data for the USGS . At that time the science of seismology was extremely new, and there were only a handful of working seismographs anywhere in the world. One was installed at the Johns Hopkins geology lab, and in 1911 Reid published

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660-671: A unique place in the history of physics for his work in making the Cavendish Laboratory perhaps the finest-ever school for training research physicists. In the fall of 1886 Reid accepted an appointment at the Case School of Applied Science in Cleveland, Ohio. He taught physics and mathematics there for eight years before being appointed an Associate at Johns Hopkins, a rank that was the equivalent of today's Assistant Professor. For reasons not yet clear, Reid did not take

715-569: Is a rare case of a passive margin slowly being transformed into an active margin . The extension of this subduction system, known as the "allochthonous unit of the Gulf of Cadiz" (AUGC), marks the continuing propagation of the Alpide belt into the Atlantic along the AGFZ. In the context of the Wilson Cycle , this suggests that the beginning of the closure of the Atlantic is taking place in front of

770-489: Is a special case of a strike-slip fault that also forms a plate boundary. Most such faults are found in oceanic crust , where they accommodate the lateral offset between segments of divergent boundaries , forming a zigzag pattern. This results from oblique seafloor spreading where the direction of motion is not perpendicular to the trend of the overall divergent boundary. A smaller number of such faults are found on land, although these are generally better-known, such as

825-464: Is also the evidence, among his surviving papers at Johns Hopkins, of an account book from Reid's early years of collecting data for the USGS (1902–14). That account book, which mostly records small amounts for secretarial expenses and the like, implies that Reid was expecting reimbursement from the USGS. He was not, however, earning a salary. Here seems a clear illustration of the turn that scientific inquiry

880-434: Is no change in length. This is due to the plates moving parallel with each other and no new lithosphere is being created to change that length. [REDACTED] [REDACTED] Decreasing length faults: In rare cases, transform faults can shrink in length. These occur when two descending subduction plates are linked by a transform fault. In time as the plates are subducted, the transform fault will decrease in length until

935-649: The American Geophysical Union from 1924-26. He corresponded with various European Societies concerned with glaciology and seismology, and in December 1926 he and his wife traveled to Japan as invited guests of an international conference on earthquake studies. Harry Fielding Reid's life bridged the gap that divided the early years of modern science, when successful men like Sir Joseph Banks and Benjamin Franklin worked on their own or financed

990-960: The Mendocino Triple Junction (Part of the Juan de Fuca plate ) off the coast of the Northwestern United States , making it a ridge-to-transform-style fault. The formation of the San Andreas Fault system occurred fairly recently during the Oligocene Period between 34 million and 24 million years ago. During this period, the Farallon plate , followed by the Pacific plate, collided into the North American plate . The collision led to

1045-594: The Netherlands during World War I. His younger brother Andrew Melville stayed in the family commodities business for some period of time but then established a second home and family in the south of France. Reid died June 18, 1944. He and his brother Andrew, along with Edith Gittings Reid and her mother, are buried in Baltimore's Greenmount Cemetery. Their markers are surrounded by the graves of various governors, mayors, Civil War generals and other representatives of

1100-561: The San Andreas Fault and North Anatolian Fault . Transform boundaries are also known as conservative plate boundaries because they involve no addition or loss of lithosphere at the Earth's surface. Geophysicist and geologist John Tuzo Wilson recognized that the offsets of oceanic ridges by faults do not follow the classical pattern of an offset fence or geological marker in Reid's rebound theory of faulting , from which

1155-444: The San Andreas Fault , and it took a massive temblor to release the strain at that point along the fault where the greatest energy had accumulated. During the previous generation European scientists had begun to wonder if faults were related to earthquakes, and vice versa, but it was Harry Fielding Reid who established that there was a clear and dynamic relationship. He called his new theory " Elastic Rebound ," and it remains even into

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1210-860: The Scotia Arc in the South Atlantic, and the Gibraltar Arc in the western Mediterranean . The Gibraltar Arc is propagating westward into the Atlantic over an east-dipping oceanic slab (one of the remainders of the Tethys Ocean ). This subduction/ back-arc basin system is developing in front of the Alboran Block (under the Alboran Sea ) at a rate faster than that of the Africa-Iberia convergence. Consequently, this area

1265-595: The Southland Syncline being split into an eastern and western section several hundred kilometres apart. The majority of the syncline is found in Southland and The Catlins in the island's southeast, but a smaller section is also present in the Tasman District in the island's northwest. Other examples include: Harry Fielding Reid Harry Fielding Reid (May 18, 1859 – June 18, 1944)

1320-667: The 21st century at the foundation of modern tectonic studies. Reid's reputation was now secure as the founding father of geophysics in the Western Hemisphere. Like his old Cambridge friend J. J. Thomson, he was acknowledged as a scientist of the first rank. There was not a Nobel Prize to win for geology, but Reid was elected to the American Philosophical Society in 1910, the National Academy of Sciences in 1912 and served as president of

1375-817: The East Pacific Ridge located in the South Eastern Pacific Ocean , which meets up with San Andreas Fault to the North. Transform faults are not limited to oceanic crust and spreading centers; many of them are on continental margins . The best example is the San Andreas Fault on the Pacific coast of the United States. The San Andreas Fault links the East Pacific Rise off the West coast of Mexico (Gulf of California) to

1430-683: The Gittings line the two Reid children were distant cousins to Wallis Warfield (born 1895-6), later Duchess of Windsor . Through his mother, Harry Fielding Reid was a great-great-grandnephew of George Washington . In addition to this social connection, the Reids were closely involved in the academic world of Baltimore, particularly figures from the “heroic” era of the Johns Hopkins Medical School, like Sir William Osler , and graduate school friends such as Woodrow Wilson . From

1485-722: The North Atlantic Ocean and is one of the oldest preserved on Earth. The western end of the AGFZ, the Azores triple junction on the Mid-Atlantic Ridge (MAR), is where the North American, African, and Eurasian plates meet. Spreading in the MAR is faster south of the AGFZ than north of it, which results in a transcurrent movement along the AGFZ at about 4 mm/a (0.16 in/year). The eastern segment of

1540-524: The Reid and Thomson families up to the present time (2007 CE). J. J. Thomson was 29 at the time they first met; Harry Fielding Reid was 26. Letters exchanged among the various family members reflect an intimacy that was born of their very early years together. Both J. J. Thomson and his son George Paget (1892–1975) went on to win Nobel Prizes for their pioneering work in subatomic physics. J. J. still holds

1595-489: The autumn of 1884 through the early summer of 1886, Reid spent time studying and traveling across Europe. During the fall of ‘84 and winter of ‘85, he may have worked at the laboratory of Hermann von Helmholtz in Berlin. His wife was with him throughout his stay, and they were joined for most of their travels by her mother, Mary Elizabeth MacGill Gittings. Mrs. Gittings left a diary, written on four small account books and now in

1650-459: The autumn of 1885, Reid, his wife and mother-in-law settled into a rented house in Cambridge, UK, and remained there for the better part of a year. Reid was soon introduced to J. J. Thomson , a young physicist who had recently been appointed to a professorship at Trinity College and made director of the Cavendish Laboratory . This friendship, both professional and personal, was to continue within

1705-460: The duration and character of such early travel is at present unknown. What is clear is that Reid eventually decided to undertake a serious study of the dynamics of glaciers, and in 1890 he organized a summertime trip to Glacier Bay in SE Alaska. He was accompanied by several young men from the Cleveland area, most of them students, one identified as H.P. Cushing. Cushing later had a long career as

Azores–Gibraltar transform fault - Misplaced Pages Continue

1760-423: The electron as a particle with both mass and charge. The 1906 San Francisco earthquake offered Reid the chance to take his interest in seismology to a new level. Andrew Lawson was then chair of the geology department at the University of California at Berkeley , and Lawson had been one of the first (1888) Hopkins Ph.D.s in geology. Perhaps through his influence Reid was chosen the only non-Californian to study

1815-584: The fault is complex and characterised by a series of seamounts and ridges separating the Tores and Horseshoe abyssal plains. The active compressional deformation in this segment is an extremely rare example of compression between two oceanic lithospheres. The Atlantic Ocean is surrounded by passive margins with the exception of three subduction zones: the Lesser Antilles Arc in the Caribbean,

1870-462: The first comprehensive treatment on the subject in English. His interest in such measuring devices may have begun in the early 1880s with his study under Henry Rowland , who was a path-breaking figure in the use of fine instruments to measure and assess nature at the atomic level. Reid's British friend and colleague, J. J. Thomson, made use of a similar interest in measurement to prove the existence of

1925-489: The great earthquake as part of a state-funded commission. Through a close examination of how different points of land along the California coast and nearby inland had moved over the course of the previous half century - here his access to USGS data was crucial - Reid was able to determine that the earthquake was a result of forces he identified as “elastic strain.” This strain had built up slowly but unequally at points along

1980-510: The job immediately but worked for one year at the newly founded University of Chicago. By the spring of 1896, however, he and his immediate family were back living in Baltimore for good, and they moved into a large townhouse on Cathedral Street, just a short distance from Mt. Vernon Place - then the heart of “Society” Baltimore - and the home of his parents. While in Cleveland, Reid had begun to study glaciology. His interest in glaciers may have begun in childhood during trips to Switzerland, although

2035-421: The mid-oceanic ridges toward the continents. Although separated only by tens of kilometers, this separation between segments of the ridges causes portions of the seafloor to push past each other in opposing directions. This lateral movement of seafloors past each other is where transform faults are currently active. Transform faults move differently from a strike-slip fault at the mid-oceanic ridge. Instead of

2090-576: The pioneering figure in modern spectral studies - gave his students. While in graduate school Reid married Edith Gittings (1861–1954). Her father, James Gittings, was descended from a long-standing Baltimore County family with strong connections to the legal and medical communities of Maryland. Her mother was Mary Elizabeth MacGill, whose father was a physician in Hagerstown, MD. Together, Reid and his wife had two children: Francis Fielding Reid, born in 1892, and Doris Fielding Reid , born in 1895. Through

2145-408: The plane of weakness, which may result in splitting in rift zones . Transform faults are commonly found linking segments of divergent boundaries ( mid-oceanic ridges or spreading centres). These mid-oceanic ridges are where new seafloor is constantly created through the upwelling of new basaltic magma . With new seafloor being pushed and pulled out, the older seafloor slowly slides away from

2200-537: The previously active transform-fault lines, which have since passed the active transform zone and are being pushed toward the continents. These elevated ridges on the ocean floor can be traced for hundreds of miles and in some cases even from one continent across an ocean to the other continent. In his work on transform-fault systems, geologist Tuzo Wilson said that transform faults must be connected to other faults or tectonic-plate boundaries on both ends; because of that requirement, transform faults can grow in length, keep

2255-405: The ridges moving away from each other, as they do in other strike-slip faults, transform-fault ridges remain in the same, fixed locations, and the new ocean seafloor created at the ridges is pushed away from the ridge. Evidence of this motion can be found in paleomagnetic striping on the seafloor. A paper written by geophysicist Taras Gerya theorizes that the creation of the transform faults between

Azores–Gibraltar transform fault - Misplaced Pages Continue

2310-434: The ridges of the mid-oceanic ridge is attributed to rotated and stretched sections of the mid-oceanic ridge. This occurs over a long period of time with the spreading center or ridge slowly deforming from a straight line to a curved line. Finally, fracturing along these planes forms transform faults. As this takes place, the fault changes from a normal fault with extensional stress to a strike-slip fault with lateral stress. In

2365-496: The second graduating class. During the following year, he entered the Hopkins Ph.D. program, which was then revolutionizing American scientific and intellectual life. Reid studied under physicist Henry Rowland and mathematician J. J. Sylvester , two of the original Johns Hopkins professors. In February 1885 Reid was granted his doctorate with a dissertation on the spectra of platinum, an assignment typical of those that Rowland -

2420-414: The sense of slip is derived. The new class of faults, called transform faults, produce slip in the opposite direction from what one would surmise from the standard interpretation of an offset geological feature. Slip along transform faults does not increase the distance between the ridges it separates; the distance remains constant in earthquakes because the ridges are spreading centers. This hypothesis

2475-602: The special collections department of the Johns Hopkins University library, that gives valuable information about their early years as a family. Among her observations was that her daughter regarded the German language as one of “sneezes and splutters.” Gittings found the wintertime climate of Berlin to be “foggy and dismal,” noted that the locals still ate dinner in mid-afternoon, and saw that some students (even visiting Americans) continued to fight duels. During

2530-463: The study done by Bonatti and Crane, peridotite and gabbro rocks were discovered in the edges of the transform ridges. These rocks are created deep inside the Earth's mantle and then rapidly exhumed to the surface. This evidence helps to prove that new seafloor is being created at the mid-oceanic ridges and further supports the theory of plate tectonics. Active transform faults are between two tectonic structures or faults. Fracture zones represent

2585-614: The subduction of the Farallon plate underneath the North American plate. Once the spreading center separating the Pacific and the Farallon plates was subducted beneath the North American plate, the San Andreas Continental Transform-Fault system was created. In New Zealand , the South Island 's Alpine Fault is a transform fault for much of its length. This has resulted in the folded land of

2640-427: The three Atlantic subduction zones. 37°N 16°W  /  37°N 16°W  / 37; -16 Transform fault A transform fault or transform boundary , is a fault along a plate boundary where the motion is predominantly horizontal . It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduction zone . A transform fault

2695-563: The transform fault disappears completely, leaving only two subduction zones facing in opposite directions. [REDACTED] [REDACTED] The most prominent examples of the mid-oceanic ridge transform zones are in the Atlantic Ocean between South America and Africa . Known as the St. Paul, Romanche , Chain, and Ascension fracture zones, these areas have deep, easily identifiable transform faults and ridges. Other locations include:

2750-577: The warmer months, but the Glacier Bay region, like most of the territory of Alaska, was otherwise a wilderness that had only had the most cursory exploration done prior to 1890. Still, Reid took a set of measurements that showed how the glaciers were moving and changing, and he proposed a theory for how the front of a glacier maintained the shape that it did. The United States Geological Survey (USGS) later named one of these glaciers for him. After returning to Baltimore, Reid devoted his next 35 years to

2805-418: The work of their friends, and a later era, from the final decades of the 19th century, when government and institutional financing caused science to become better organized even as it was made into a more bureaucratic enterprise. Reid's long trip to Europe from 1884 to 1886 appears to have been financed by his father, or so it appears from a letter his wife later wrote (in the fall of 1886) to J. J. Thomson. There

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2860-491: Was a descendant of Betty Washington Lewis, sister of George Washington ; his father was a successful sugar merchant. The younger Reid's early education took him for at least one year to Switzerland; he is also known to have attended and graduated from the Pennsylvania Military Academy . In 1877 Reid enrolled at the newly founded Johns Hopkins University , from which he earned a A.B. in 1880 as part of

2915-405: Was an American geophysicist . He was notable for his contributions to glaciology and seismology , particularly his theory of elastic rebound that related faults to earthquakes . He was a professor of dynamical geology and geography at the Johns Hopkins University. Harry Fielding Reid was born in Baltimore, the fourth of seven children of Andrew and Fanny Brooke Gwathmey Reid. Reid's mother

2970-458: Was confirmed in a study of the fault plane solutions that showed the slip on transform faults points in the opposite direction than classical interpretation would suggest. Transform faults are closely related to transcurrent faults and are commonly confused. Both types of fault are strike-slip or side-to-side in movement; nevertheless, transform faults always end at a junction with another plate boundary, while transcurrent faults may die out without

3025-511: Was taking by 1902: there was evidently no regular income involved, yet Reid was not expected to foot the bill entirely on his own. Government subsidy – also taking place at Johns Hopkins as the geology faculty did work for the Maryland State Highway Department after 1898 – also meant greater accountability: hence Reid's careful recording of expenses. Beginning in at least 1896 with the death of his father, Reid had

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