Wilbur Zelinsky

Wilbur Zelinsky, professor emeritus at Penn State University, died on May 4, 2013, at age 91. He was born in Chicago, Illinois in 1921. Described as a cultural geography icon and explorer of American life and significance, he used his eyes to observe the differences in human landscape, while studying and using data to find deeper information. He inspired countless students to examine culture, literature and music.

From 1959-1973, he held many levels of leadership roles for the Association of American Geographers, including president from 1972-1973.

During his career, AAG recognized his contributions and achievements. In 2006, Zelinsky was given the AAG Presidential Achievement Award for his long and distinguished career in geography; for the influence of his publications across a wide range of topics in human geography; and for his early and fervent support for the incorporation of more women into the discipline. He received the AAG John Brinckerhoff Jackson Prize in 1992 for his book, The Cultural Geography of the United States. And in 1966, the association awarded him Honors for Meritorious Contributions.

During AAG’s 2005 annual meeting, the Cultural Geography Specialty Group honored him at special sessions (I and II). The contents of those seminars resulted in a special tribute issue of The Geographical Review.

Joseph Wood, professor and provost at the University of Baltimore once noted, “For six decades Wilbur Zelinsky has been an original and authentic voice in American cultural geography. His curiosity is endless, his intellectual appetite voracious. He seeks human meaning in every facet of material life and every corner of the American scene.”

Among Zelinsky's many awards, he also received a Guggenheim Fellowship for geography and environmental studies in the social sciences in 1980 and the Cullum Geographical Medal of the American Geographical Society in 2001.

His large body of work includes more than 200 books, atlases, chapters, articles, reviews, reports and other writings.

He received his bachelor’s degree in 1944 and his doctorate in 1953 from the University of California, Berkeley. He graduated from the University of Wisconsin in 1946 with a master’s degree.

During World War II, he served as a map draftsman with several companies. He then worked as a terrain analyst for the U.S. Army Corps of Engineers in occupied Germany. After the war, Zelinsky accepted an appointment from 1948 to 1952 at the University of Georgia. From 1952-1954, he returned to the University of Wisconsin as a researcher.

From the mid- to late-50s, he was an industrial location analyst for the Chesapeake & Ohio Railway during which time he also was an adjunct professor at Wayne State University. He then taught at Southern Illinois University for a few years before joining the department of geography at Penn State University in 1963. He remained there for the duration of his career.

Zelinsky’s research and scholarship linked many people and disciplines. His work in the 1960s with Penn State professors of sociology, economics and anthropology created a population research center, which would later become the Graduate Program in Demography. From 1972-1973, he served as the first director of what is now the Population Research Institute. He also served as chair of the geography department and was a fixture at the weekly Coffee Hour promoting interdisciplinary scholarship and collegiality.

Peirce F. Lewis, professor emeritus at Penn State once wrote, "… Wilbur Zelinsky had been an icon to me long before I ever met him—and that was back in the early 1960s. In fact, Wilbur Zelinsky was one of the few icons that I knew about in geography, although I did not think to call him that. To me … Zelinsky's insight seemed a vision from on high."

He also played the violin. In 1967, he performed during the State College Music Guild’s first concert featuring Bach’s Brandenberg Concerto No. 5 at the Central Pennsylvania Festival of the Arts. Although the group has changed it’s name to the Nittany Valley Symphony since that first concert, Zelinsky had continued to play in the violin section right up through the February 16, 2013, concert featuring “Bohemian Rhapsody.”

Symphony Executive Director Roberta Strebel remarked, “It’s funny, you know. I never really thought of Wilbur as being a long-time professor of geography. I always thought of him as a violinist.”

Zelinsky’s lifelong explorations connected people both personally and professionally. The field of cultural geography and the greater communities in which he participated will continue to be stimulated by his example.

Aziz Ab'Sáber

Aziz Nacib Ab'Sáber; October 24, 1924 – March 16, 2012) was a geographer and one of Brazil's most respected scientists, honored with the highest awards of Brazilian science in geography, geology, ecology and archaeology. Graduated in geography, he was a president and honorary president of the Sociedade Brasileira para o Progresso da Ciência (Brazilian Society for the Advancement of Science), Emeritus Professor of the University of São Paulo and member of the highest rank - Order Grão-Cruz in Earth Sciences - of the Academy of Science. Among the awards, he has received the UNESCO Prize on Science and the Environment in 2001 and the Prize to the Intellectual of Brazil in 2011.

The contributions of Ab'Saber to science range from the first research of oil camps in Brazil's northeast to surveys of Brazil's natural realms and the restoration of the history of forests, camps and primitive humans over geologic time in South America. He made central contributions to biology, South American archaeology, and to Brazilian ecology, geology and geography. He has published more than 480 works, most of them scientific publications. Among his scientific proposals are FLORAM, the Code of biodiversity and his theory of refuges related to the Amazones.

Ab'Sáber was the first person to classify scientifically the Brazilian and South-America territory in morphoclimatic domains. He also contributed to the "Pleistocene refuge hypothesis", an attempt to explain the distribution of Neotropical taxa as a function of their isolation in forest fragments during glacial periods, which allowed populations to speciate. He died in 2012 following a heart attack.

Milton Santos

Milton Almeida dos Santos (May 3, 1926 – June 24, 2001) was a Brazilian geographer and geography scholar who had a degree in law. He became known for his pioneering works in several branches of geography, notably urban development in developing countries. He is considered the father of critical geography in Brazil. Santos was a recipient of the Vautrin Lud Prize, often seen as geography's equivalent of the Nobel Prize, and a posthumous recipient of the Prêmio Anísio Teixeira, awarded every five years by the Brazilian agency for the improvement of higher education personnel to distinguished contributors to research and development in Brazil.

Biography

Santos was born in Brotas de Macaúbas, Bahia, Brazil on May 3, 1926. His parents were elementary school teachers who home-schooled him. His Black paternal grandfather had been formerly enslaved. By the time Santos was eight, he was through with his elementary education. From 1934 to 1936, he lived in Alcobaça, where he went to study French and "good manners".

Santos taught geography and math to fellow high-school students in order to finance his pre-law in Salvador. He graduated in law from the Federal University of Bahia but decided not to practice, becoming instead a high-school geography teacher in Ilhéus. There, he met and married his first wife Jandira, who gave birth to their son Milton filho. Also in Ilhéus, Santos worked on the side as a journalist for the A Tarde newspaper.

Santos studied and taught in Europe, the Americas, and Africa. He completed his PhD at the University of Strasbourg in 1958 under Jean Tricart. Prior to being exiled by the Brazilian military dictatorship, he was forbidden to leave the country and could do so only after a negotiation between the French ambassador and the government. He managed to turn an otherwise painful thirteen-year exile into a successful international career. He lived in Bordeaux and Toulouse, where he met geography student Hélène, who was to become his second wife and give birth to son Rafael. He also taught in Paris at the Sorbonne, Toronto and the MIT, where he teamed up with Noam Chomsky.

Santos wrote more than forty books, all told, in several languages. His works became a reference for those interested in understanding geography from a critical point of view (if not necessarily in a negative light), especially by applying concepts of the Frankfurt School. His main concerns were connected on the one hand to city structure, urban networks and urbanisation processes in developing nations; and on the other hand, to the epistemology of geography (which means, its object and relationship to other sciences, such as economics and ethnography). His views about space helped geography transition from a concept of space as a stage for human action, to a constraint on human action.

His works include "Por uma Geografia Nova" (For a New Geography) (1978) and "A natureza do espaço" (The Nature of Space) (1996). His work "O espaço dividido" (The Shared Space), in which Santos develops a theory of urban development in developing countries, is considered a geography classic.

In 1994, Santos was awarded the Vautrin Lud Prize, the highest prize in geography. The Prize is modelled after the Nobel Prize and colloquially called the Nobel Prize for geography. To date, Santos remains the only Latin-American scholar to ever win it.

Santos died in São Paulo, on June 24, 2001, at age 75, as a result of prostate cancer diagnosed about seven years earlier.

Bertha Becker

Bertha Koiffmann Becker (November 7, 1930 – July 13, 2013) was a Brazilian geographer, author and professor emeritus at the Federal University of Rio de Janeiro. She published more than 180 books, articles, and other works during her career. Much of her research dealt with issues affecting the Amazon rainforest and surrounding regions, as well as the political geography of Brazil. She helped develop new public policies for the Brazilian Ministry of Science and Technology. She spoke as a panelist at the United Nations Conference on Sustainable Development Rio+20 in 2012.

Bertha Koiffmann Becker.

Born in Rio de Janeiro, Becker received her degrees from the University of Brazil in 1952 in geography and history. In 1970, she completed her doctorate at the Federal University of Rio de Janeiro, where she became a longtime faculty member. She also completed her post-doctoral studies in urban studies and planning at the Massachusetts Institute of Technology in the United States.

Becker served as the Vice President of the International Geographical Union from 1996 to 2000 and the Vice President of the International Advisory Group of the Pilot for the Protection of Tropical Forests from 1995 to 2005. She was awarded the David Livingstone Centenary Medal from the American Geographical Society, an honorary doctorate from the University of Lyon, and the Carlos Chagas Filho Scientific Merit award. In 2006, she had been elected a member of the Brazilian Academy of Sciences.

Bertha Becker died in Rio de Janeiro on July 13, 2013, at the age of 82.

Icelandite

Icelandite is a type of volcanic rock, an iron rich, aluminium lacking andesite. Icelandites are between rhyodacite and tholeiitic basalt in composition and contain andesine, hypersthene and augite, with a silica (SiO2) content greater than 60%.

The name was coined by the British geologist Ian S. E. Carmichael (who later became professor at the University of California, Berkeley) while working around 1960 on his PhD thesis at a Cenozoic volcano near the parsonage Thingmuli (Þingmúli) in East Iceland. For continental cogenetic series of volcanic rocks it is generally the case that the concentration of iron decreases with increasing silica content, but at Þingmúli the opposite was true, leading Carmichael to the conclusion that the iron-rich intermediate rock deserved its own name, icelandite.

Anorthosite

Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present. 

Anorthosites are of enormous geologic interest, because it is still not fully understood how they form. Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense than magma; so, as plagioclase crystallizes in a magma chamber, the plagioclase crystals float to the top, concentrating there. 

Anorthosite on Earth can be divided into five types: 

1. Archean-age anorthosites

2. Proterozoic anorthosite (also known as massif or massif-type anorthosite) – the most abundant type of anorthosite on Earth 

3. Layers within Layered Intrusions (e.g., Bushveld and Stillwater intrusions)

4. Mid-ocean ridge and transform fault anorthosites

5 . Anorthosite xenoliths in other rocks (often granites, kimberlites, or basalts) 

Of these, the first two are the most common. These two types have different modes of occurrence, appear to be restricted to different periods in Earth's history, and are thought to have had different origins. Lunar anorthosites constitute the light-coloured areas of the Moon's surface and have been the subject of much research.

Slate

Slate is a low grade metamorphic rock generally formed by the metamorphosis of mudstone / shale, or sometimes basalt, under relatively low pressure and temperature conditions. Clay minerals in the parent rock metamorphose into mica minerals ( biotite, chlorite, muscovite) which are aligned along foliation planes perpendicular to the direction of pressure. Slate is characterized by fine foliation along which it breaks to leave smooth, flat surfaces (often referred to as "slaty cleavage" - not to be confused with cleavage in minerals). Sometimes relict (original) bedding is visible on foliation planes. Slate will 'ring' when struck, unlike mudstone or shale which makes a dull 'thud'.

Phyllite, a metamorphic rock very similar to slate, has undergone a slightly greater degree of metamorphism. It is slightly coarser-grained (some crystals may be visible to the naked eye), and the foliation is less perfect (it lacks perfect "slaty cleavage").

Texture - foliated, foliation on a mm scale.

Grain size - very fine-grained; crystals not visible to the naked eye.
Hardness - hard and brittle.
Colour - variable - black, shades of blue, green, red, brown and buff.
Mineralogy - contains mica minerals ( biotite, chlorite, muscovite) which typically impart a sheen on foliation surfaces; can contain cubic pyrite porphyroblasts.
Other features - smooth to touch.
Uses - historically extensively used for roof and floor tiles, and blackboards; standard material for the beds of pool / snooker / billiard tables.

Schist

Schist is medium grade metamorphic rock, formed by the metamorphosis of mudstone / shale, or some types of igneous rock, to a higher degree than slate, i.e. it has been subjected to higher temperatures and pressures. The resulting foliation is coarser and more distinct than that of slate due to the higher degree of crystallisation of mica minerals ( biotite, chlorite, muscovite) forming larger crystals, and is often referred to as schistosity. These larger crystals reflect light so that schist often has a high lustre, i.e. it is shiny. Porphyroblasts are common in schist, and they provide information on the temperature and pressure conditions under which the rock formed. Due to the more extreme formation conditions, schist often shows complex folding patterns. There are many varieties of schist and they are named for the dominant mineral comprising the rock, e.g. mica schist, green schist (green because of high chlorite content), garnet schist etc.

Texture - foliated, foliation on mm to cm scale.
Grain size - fine to medium grained; can often see crystals with the naked eye.
Hardness - generally hard.
Colour - variable - often alternating lighter and darker bands, often shiny.
Mineralogy - mica minerals ( biotite, chlorite, muscovite), quartz and plagioclase often present as monomineralic bands, garnet porphyroblasts common.
Other features - generally smoothish to touch.
Uses - generally used as a decorative rock, e.g. walls, gardens etc; high percentage of mica group minerals precludes its use in the construction and roading industries.

Quartzite

Quartzite is a metamorphic rock formed when quartz-rich sandstone or chert has been exposed to high temperatures and pressures. Such conditions fuse the quartz grains together forming a dense, hard, equigranular rock. The name quartzite implies not only a high degree of induration (hardness), but also a high quartz content. Quartzite generally comprises greater than 90% percent quartz, and some examples, containing up to 99% quartz, and are the largest and purest concentrations of silica in the Earth's crust. Although a quartz-rich sandstone can look similar to quartzite, a fresh broken surface of quartzite will show breakage across quartz grains, whereas the sandstone will break around quartz grains. Quartzite also tends to have a sugary appearance and glassy lustre. The variety of colours displayed by quartzite are a consequence of minor amounts of impurities being incorporated with the quartz during metamorphism. Although quartzite can sometimes appear superficially similar to marble, a piece of quartzite will not be able to be scratched by a metal blade, and quartzite will not fizz on contact with dilute hydrochloric acid.

Texture - granular.
Grain size - medium grained; can see interlocking quartz crystals with the naked eye.
Hardness - hard.
Colour - variable - pure quartzite is white but quartzite exists in a wide variety of colours.
Mineralogy - quartz.
Other features - generally gritty to touch.
Uses - pure quartzite is a source of silica for metallurgical purposes, and for the manufacture of brick; as aggregate in the construction and roading industries; as armour rock for sea walls; dimension stone for building facings, paving etc.

Mylonite

Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism. This process involves nearly complete pulverisation of the parent rock so the original minerals are almost completely broken down and recrystallise as smaller grains which are tightly intergrown, forming a dense, hard rock. As a result of the shearing encountered during formation, recrystallised minerals grow preferentially along planes of foliation parallel to the direction of shear. Mylonite may also be characterised by the smearing, flattening or rotation of any porphyroblasts formed during metamorphism. Not surprisingly, the word mylonite is derived from the Greek word for mill.

Texture - foliated.
Grain size - very fine grained; grains need to be observed under a microscope; sometimes contains porphyroblasts.
Hardness - hard.
Colour - variable, grey to black, but can form in a variety of colours dependent on parent rock composition.
Mineralogy - extremely variable, dependent on the original composition of the parent rock.
Other features - generally smooth to touch.
Uses - as aggregate in the construction and roading industries.

Marble

Marble is a metamorphic rock formed when limestone is exposed to high temperatures and pressures. Marble forms under such conditions because the calcite forming the limestone recrystallises forming a denser rock consisting of roughly equigranular calcite crystals. The variety of colours exhibited by marble are a consequence of minor amounts of impurities being incorporated with the calcite during metamorphism. While marble can appear superficially similar to quartzite, a piece of marble will be able to be scratched by a metal blade, and marble will fizz on contact with dilute hydrochloric acid.

Texture - granular.
Grain size - medium grained; can see interlocking calcite crystals with the naked eye.
Hardness - hard, although component mineral is soft (calcite is 3 on Moh's scale of hardness).
Colour - variable - pure marble is white but marble exists in a wide variety of colours all the way through to black .
Mineralogy - calcite.
Other features - generally gritty to touch.
Uses - building stone; dimension stone for building facings, paving etc; cut into blocks and cut for monuments, headstones etc (wears over time due to softness of calcite, prone to acid rain damage [calcite is soluble in acid]); whiting material in toothpaste, paint and paper.

Hornfels

Hornfels is a metamorphic rock formed by the contact between mudstone / shale, or other clay-rich rock, and a hot igneous body, and represents a heat-altered equivalent of the original rock. This process is termed contact metamorphism. Because pressure is not a factor in the formation of hornfels, it lacks the foliation seen in many metamorphic rocks formed under high pressure and temperature regimes. Pre-existing bedding and structure of the parent rock is generally destroyed during the formation of hornfels. It is often difficult to identify hornfels without microscopic observation, or knowledge of its association with a magma body, as it is typically non-descript in hand specimen. Under a microscope the structure of hornfels is very distinctive, with small, generally equigranular, mineral grains fitting closely together like the fragments of a mosaic or a rough pavement.

Texture - granular, platy or elongate crystals randomly oriented so no foliation evident.

Grain size - very fine grained; grains need to be observed under a microscope; can contain rounded porphyroblasts.
Hardness - hard (commonly displays conchoidal fracture).
Colour - variable, generally grey to black, but can form in a variety of colours dependent on parent rock composition.
Mineralogy - extremely variable, dependent on the original composition of the parent rock; generally contains minerals only formed under high temperature conditions, e.g. andalusite (Al ₂SiO ₅), cordierite ((Mg, Fe) ₂Al ₄Si ₅O ₁₈).
Other features - generally smooth to touch.
Uses - as aggregate in the construction and roading industries.

Gneiss

Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of granite, or sedimentary rock. Gneiss displays distinct foliation, representing alternating layers composed of different minerals. However, unlike slate and schist, gneiss does not preferentially break along planes of foliation because less than 50% of the minerals formed during the metamorphism are aligned in thin layers. Because of the coarseness of the foliation, the layers are often sub-parallel, i.e. they do not have a constant thickness, and discontinuous.

Gneiss is typically associated with major mountain building episodes. During these episodes, sedimentary or felsic igneous rocks are subjected to great pressures and temperatures generated by great depth of burial, proximity to igneous intrusions and the tectonic forces generated during such episodes. Gneisses from western Greenland comprise the oldest crustal rocks known (more than 3.5 billion years old). Gneiss is an old German word meaning bright or sparkling.

Texture - foliated, foliation on a scale of cm or more.
Grain size -medium to coarse grained; can see crystals with the naked eye.
Hardness - hard.
Colour - variable - generally alternating lighter and darker sub-parallel discontinuous bands.
Mineralogy - felsic minerals such as feldspar ( orthoclase, plagioclase) and quartz generally form the light coloured bands; mafic minerals such as biotite, pyroxene ( augite) and amphibole ( hornblende) generally form the dark coloured bands; garnet porphyroblasts common.
Other features - generally rough to touch.
Uses - dimension stone for building facings, paving etc.

Sandstone

Sandstone is a sedimentary rock formed from cemented sand-sized clasts. The cement that binds the clasts can vary from clay minerals to calcite, silica or iron oxides. Sandstone can be further divided according to:

Clast size - fine (0.06-0.2mm), medium (0.2-0.6mm), coarse (0.6-2mm);

Sorting - a sandstone comprising a mixture of clast sizes is poorly sorted, while one comprising mostly clasts of the same size is well sorted; a sandstone containing very little silt and / or clay is termed arenaceous; a sandstone containing a significant amount of silt and / or clay is termed argillaceous or a "wacke" (see greywacke for more information);

Mineral content - a sandstone consisting of more than 25% feldspar clasts is termed arkose; a sandstone consisting of more than 90% quartz clasts is called quartzose;

Texture - clastic (only noticeable with a microscope).

Grain size - 0.06 - 2mm; clasts visible to the naked eye, often identifiable.
Hardness - variable, soft to hard, dependent on clast and cement composition.
Colour - variable through grey, yellow, red to white reflecting the variation in mineral content and cement.
Clasts - dominantly quartz and feldspar ( orthoclase, plagioclase) with lithic clasts and varying minor amounts of other minerals.
Other features - gritty to touch (like sandpaper).
Uses - if soft then generally of no use; if hard then can be used as aggregate, fill etc. in the construction and roading industries; dimension stone for buildings, paving, etc.

Mudstone

Mudstone is an extremely fine-grained sedimentary rock consisting of a mixture of clay and silt-sized particles. Terms such as claystone and siltstone are often used in place of mudstone, although these refer to rocks whose grain size falls within much narrower ranges and under close examination these are often technically mudstones. Shale is often used to describe mudstones which are hard and fissile (break along bedding planes). Marl is often used to describe carbonate-rich soft mudstones.

Texture - clastic (only noticeable with a microscope).
Grain size - very fine-grained (< 0.06mm); clasts not visible to the naked eye.
Hardness - generally quite soft, but can be hard and brittle.
Colour - variable - black, white, grey, brown, red, green, blue etc.
Clasts - generally a mixture of clay minerals with any or all of quartz, feldspar ( orthoclase, plagioclase), mica ( biotite, chlorite, muscovite); can contain iron oxides (cause red or yellowish colouring); black colouring due to carbonaceous content and / or pyrite.
Other features - smooth to touch.
Uses - generally too soft to be of use.

Limestone

Limestone is a sedimentary rock consisting of more than 50% calcium carbonate ( calcite - CaCO ₃). There are many different types of limestone formed through a variety of processes. Limestone can be precipitated from water ( non-clastic, chemical or inorganic limestone), secreted by marine organisms such as algae and coral (biochemical limestone), or can form from the shells of dead sea creatures (bioclastic limestone). Some limestones form from the cementation of sand and / or mud by calcite ( clastic limestone), and these often have the appearance of sandstone or mudstone. As calcite is the principle mineral component of limestone, it will fizz in dilute hydrochloric acid.

Texture - clastic or non-clastic.
Grain size - variable, can consist of clasts of all sizes.
Hardness - generally hard.
Colour - variable, but generally light coloured, grey through yellow.
Clasts - if clastic / bioclastic then grains and / or broken or whole shell fragments visible; if non-clastic / chemical then crystalline and no clasts visible.
Other features - smooth to rough to touch, dependent on composition and / or mode of formation.
Uses - base for cement; as dimension stone for decoration of walls and floors; in the production of lime fertilizer, paper, petrochemicals, pesticide, glass etc.

Edward Soja

Edward William Soja (1940–2015) was a self-described "urbanist," a noted postmodern political geographer and urban theorist on the planning faculty at UCLA, where he was Distinguished Professor of Urban Planning, and the London School of Economics. He had a Ph.D. from Syracuse University. His early research focused on planning in Kenya, but Soja came to be known as the world's leading spatial theorist with a distinguished career writing on spatial formations and social justice.

In 2015 he was awarded the Vautrin Lud Prize, the highest honor for a geographer and often called the Nobel Prize in the field of geography.

In addition to his readings of American feminist cultural theorist bell hooks (b. 1952), and French intellectual Michel Foucault (1926–1984), Soja's greatest contribution to spatial theory and the field of cultural geography is his use of the work of French Marxist urban sociologist Henri Lefebvre (1901–1991), author of The Production of Space (1974). Soja updated Lefebvre's concept of the spatial triad with his own concept of spatial trialectics which includes thirdspace, or spaces that are both real and imagined.

Soja focuses his critical postmodern analysis of space and society, or what he calls spatiality, on the people and places of Los Angeles. In 2010 the University of Minnesota Press released his work on spatial justice, which was followed in 2014 with his My Los Angeles published by the University of California Press. He also published in the critical urban theory journal City: analysis of urban trends, culture, theory, policy, action.

Soja collaborated on research and writing with, most notably, Allen J. Scott (UCLA), Michael Storper (UCLA, London School of Economics), Fredric Jameson (Duke University), David Harvey (Johns Hopkins, CUNY), Kurt Iveson (University of Sydney), and various faculty in the departments of Urban Planning, Architecture, Policy Studies, and Geography at UCLA.

Soja served as the doctoral academic advisor to many leading scholars in the field of urban theory and geography including Professor Mustafa Dikec (École d'Urbanisme de Paris), Dr. Walter J. Nicholls (University of California, Irvine), Dr. Mark Purcell (University of Washington), Dr. Diane Davis (Harvard University), Dr. Juan Miguel Kanai (University of Sheffield) and Dr. Stefano Bloch (University of Arizona).

Conglomerate

Conglomerate is a sedimentary rock formed from rounded gravel and boulder sized clasts cemented together in a matrix. The rounding of the clasts indicates that they have been transported some distance from their original source (e.g. by a river or glacier), or that they have resided in a high energy environment for some time (e.g. on a beach subject to wave action). The cement that binds the clasts is generally one of either calcite, silica or iron oxide. The matrix can consist solely of the cementing material, but may also contain sand and / or silt sized clasts cemented together among the coarser clasts. Conglomerates can be further divided according to:

Class - conglomerate can be divided into two broad classes:

Clast supported - where the clasts touch each other and the matrix fills the voids; and

Matrix supported - where the clasts are not in contact and the matrix surrounds each clast;

Clast size - fine (2 - 6mm), medium (6 - 20mm), coarse (20 - 60mm), very coarse (> 60mm);

Sorting - a conglomerate comprising a mixture of clast sizes is poorly sorted, while one comprising mostly clasts of the same size is well sorted;

Lithology - a conglomerate where the clasts represent more than one rock type is termed polymictic (or petromictic), while one where the clasts are of a single rock type are monomictic (or oligomictic)

Texture - clastic (coarse-grained).
Grain size - > 2mm; clasts easily visible to the naked eye, should be identifiable.
Hardness - variable, soft to hard, dependent on clast composition and strength of cement.
Colour - variable, dependent on clast and matrix composition.
Clasts - variable, but generally harder rock types and / or minerals dominate.
Other features - clasts generally smooth to touch, matrix variable.
Uses - as dimension stone for decoration of walls and floors; if hard can be used as aggregate, fill etc. in the construction and roading industries.

Chert

Chert is a sedimentary rock consisting almost entirely of silica (SiO ₂), and can form in a variety of ways. Biochemical chert is formed when the siliceous skeletons of marine plankton are dissolved during diagenesis, with silica being precipitated from the resulting solution. Replacement chert forms when other material is replaced by silica, e.g. petrified wood forms when silica rich fluids percolate through dead wood and the silica precipitates to replace the wood. Chert can also form through direct precipitation from silica rich fluids, e.g. agate is formed by the precipitation of silica in voids within a rock. Chert has the general physical properties of quartz.

Texture - non-clastic.
Grain size - cryptocrystalline, cannot be seen except under very high magnification.
Hardness - hard.
Colour - all colours, dependent on impurities present when precipitated.
Clasts - none.
Other features - smooth to touch, glassy, exhibits conchoidal fracture.
Uses - mainly decorative; ancient cultures used chert for cutting tools, arrow heads etc.

Breccia

Breccia is a rock formed from angular gravel and boulder-sized clasts cemented together in a matrix. The angular nature of the clasts indicates that they have not been transported very far from their source. There are several modes of formation for breccia. Some represent consolidated material accumulated on steep hill slopes or at the foot of cliffs. Cataclastic breccias are produced by the fragmentation of rocks during faulting. Volcanic breccias (agglomerates) comprise blocks of lava in an ash matrix and are the product of an explosive eruption. Hydrothermal breccias are formed when hydrothermal fluid fractures a rock mass. Impact breccias are formed when a meteor impacts the Earth's surface, fracturing rock at the site of the impact. The cement that binds the clasts in a breccia is generally one of either calcite, silica or iron oxide. The matrix can consist solely of the cementing material, but may also contain sand and / or silt sized clasts cemented together among the coarser clasts. Breccia can be further divided according to:

Class - breccia can be divided into two broad classes:

Clast supported - where the clasts touch each other and the matrix fills the voids; and

Matrix supported - where the clasts are not in contact and the matrix surrounds each clast;

Clast size - fine (2 - 6mm), medium (6 - 20mm), coarse (20 - 60mm), very coarse (> 60mm);

Sorting - a breccia comprising a mixture of clast sizes is poorly sorted, while one comprising mostly clasts of the same size is well sorted;

Lithology - a breccia where the clasts represent more than one rock type is termed polymictic (or petromictic), while one where the clasts are of a single rock type are monomictic (or oligomictic).

Texture - clastic (coarse-grained).

Grain size - > 2mm; clasts easily visible to the naked eye, should be identifiable.
Hardness - variable, soft to hard, dependent on clast composition and strength of cement.
Colour - variable, dependent on clast and matrix composition.
Clasts - variable, but generally harder rock types and / or minerals dominate.
Other features - rough to touch due to angular clasts.
Uses - as dimension stone for decoration of walls and floors; if hard can be used as aggregate, fill etc. in the construction and roading industries.