More than two thirds of the continental regions are in the Northern Hemisphere, rimming the Arctic Ocean. South America and Africa project into the Southern Hemisphere as southward-pointing triangles, forming extensive peninsular regions separating the Atlantic, Pacific, and Indian oceans. In addition, the continents are generally antipodal to the ocean basins (i.e., ocean basins are found on the opposite side of the earth from continental masses). For example, there is an antipodal relationship between the continental Antarctic region and the Arctic Ocean, and the Pacific Ocean lies opposite Africa and Europe. The continental areas above sea level comprise about 29% of the earth's surface. However, from a geological point of view, a submerged continental shelf is also part of a continent. Inclusion of the shelf area increases the extent of the continents to 35% of the globe. The earth's average land elevation is c.2,700 ft (820 m) above sea level; the highest point is the summit of Mt. Everest at 29,035 ft (8,850 m); and the lowest point is the shore of the Dead Sea at 1,345 ft (410 m) below sea level.
Geologically and topographically the continents are exceedingly complex and variable in detail, yet certain large-scale structural and topographic features appear to be common to all. The continents are composed mainly of granitic rocks and measure an average of 25 mi (40 km) thick. Underlying the ocean are denser basaltic rocks measuring about 4 mi (7 km) thick. Basaltic rocks may also form the lower portions of the continental crust in many regions. The upper and lower crust zones deform by different mechanisms; the upper crust is brittle and deforms by faulting (see fault) while the lower crust is ductile and capable of flow. The crust and the solid upper mantle form the lithosphere.Plateaus, Shields, and Mountains
Generally, the continents contain vast interior plains or plateaus, underlain by a basement complex of igneous and metamorphic rocks of Precambrian age. In some places, the basement complex is exposed at the surface, where it is often called the shield, or craton. The interior of shield areas contain some of the oldest rocks known on the earth's surface. The Canadian Shield area of E Canada is the exposed basement complex of North America. Portions of shield areas are covered with veneers of flat-lying sedimentary rocks of younger age. The interior plains of the continents are frequently bounded on one or more sides by ranges of mountains. These mountains have been intricately folded and faulted. They also display abundant evidence of volcanic activity, large-scale igneous intrusions, and deformation structures associated with convergent plate movement. In the United States the folded Appalachian Mts. lie to the east of the interior plains and were caused mainly by the collision of two continents. The Rocky Mts. are to the west, formed by huge igneous masses that pushed upward through overlying sedimentary rocks, which were then eroded away.Floating Continents and Isostasy
Evidence indicates that part of the mantle below the crust consists of semifluid rocks on which the continents and ocean basins, in effect, are floating. A condition of gravitational balance, called isostasy, exists between different parts of the earth's crust. The theory of isostasy claims that the continental crust floats higher than the oceanic crust because the former is composed of a thick layer of lower density rocks while the latter is composed of a thin layer of higher density rocks. Isostatic adjustments to changes in mass distribution on the earth's surface associated with plate interactions may occur through flow of semifluid materials deep in the earth. These materials cause a compensatory uplift of mountains and plateau areas as erosion wears them down. The mass of eroded material is added to and thus depresses the continental shelves and the ocean floor. Adjustments also accompany such changes as the growth and melting of continental ice sheets.
The oldest continental rocks dated by radioactivity are 3.98 billion years old, which suggests that the continents and oceans are probably permanent features of the earth's surface. Although the continental regions have been periodically covered by shallow seas, they appear never to have been the sites of deep oceans. How the continents originated has been a major debate in geology. The 19th-century geologist J. D. Dana proposed the continent accretion theory where the continents have always been stationary, with the gradual addition of new material around a central nucleus. Another theory was called the continental assimilation hypothesis, where the ocean areas accumulate the denser elements, then subside to form basins. In the late 19th cent., George Darwin proposed that the moon was gravitationally extracted from the Pacific Ocean, with the earth eventually redistributing into oceanic and continental crusts. In 1925, the expansion of the earth hypothesis stated that the present continents split apart as the earth expanded, noting that the continents could cover a sphere half the surface area of the present earth. Accepted theory now points to continental drift and seafloor spreading as a result of plate tectonics.
Though Lemuria has passed out of the realm of conventional science, it has been adopted by writers involved in the occult, as well as some Tamil writers of India. Accounts of Lemuria differ, but all share a common belief that a continent existed in ancient times and sank beneath the ocean as a result of a geological, often cataclysmic, change.
Sclater's theory was hardly unusual for his time. The acceptance of Darwinism led scientists to seek to trace the diffusion of species from their points of evolutionary origin. Prior to the acceptance of continental drift, biologists frequently postulated submerged land masses in order to account for populations of land-based species now separated by barriers of water. Similarly, geologists tried to account for striking resemblances of rock formations on different continents. The first systematic attempt was made by Melchior Neumayr in his book Erdgeschichte in 1887. Many hypothetical submerged land bridges and continents were proposed during the 19th century, in order to account for the present distribution of species.
After gaining some acceptance within the scientific community, the concept of Lemuria began to appear in the works of other scholars. Ernst Haeckel, a German Darwinian taxonomist, proposed Lemuria as an explanation for the absence of "missing link" fossil records. According to another source, Haeckel put forward this thesis prior to Sclater (but without using the name 'Lemuria'). Locating the origins of the human species on this lost continent, he claimed the fossil record could not be found because it had sunk beneath the sea.
The Lemuria theory disappeared completely from conventional scientific consideration after the theories of plate tectonics and continental drift were accepted by the larger scientific community. According to the theory of plate tectonics (now the only accepted paradigm in geology), Madagascar and India were indeed once part of the same landmass (thus accounting for geological resemblances), but plate movement caused India to break away millions of years ago, and move to its present location. The original landmass broke apart - it did not sink beneath sea level.
In 1999, drilling by the JOIDES Resolution research vessel in the Indian Ocean discovered evidence that a large island, the Kerguelen Plateau, was submerged about 20 million years ago by rising sea levels. Samples showed pollen and fragments of wood in a 90 million-year-old sediment. Although this discovery might encourage scholars to expect similarities in dinosaur fossil evidence, and may contribute to understanding the breakup of the Indian and Australian land masses, it does not support the concept of Lemuria as a land bridge for mammals.
Within Blavatsky's complex cosmology, which includes seven "Root Races", Lemuria was occupied by the "Third Root Race", described as about seven foot tall, sexually hermaphroditic, egg-laying, mentally undeveloped and spiritually more pure than the following "Root Races". Before the coming of the Lemurians, the second "Root Race" is said to have dwelled in Hyperborea. After the subsequent creation of mammals, Mme Blavatsky revealed to her readers, some Lemurians turned to bestiality. The gods, aghast at the behavior of these "mindless" men, sank Lemuria into the ocean and created a "Fourth Root Race"—endowed with intellect—on Atlantis.
One of the most elaborate accounts of lost continents was given by the later theosophical author William Scott Elliott. The English theosophist said he received his knowledge from the Theosophical Masters by "astral clairvoyance." In 1896, in "The Story of Atlantis & The Lost Lemuria", he described the continent of Lemuria as stretching from the east coast of Africa across the Indian and the Pacific Oceans.
James Bramwell described Lemuria in his book, Lost Atlantis, as “a continent that occupied a large part of what is now the South Pacific Ocean.” Quoting Story of Atlantis, by William Scott-Elliott; “Atlantis, according to Scott-Elliott’s first map, which shows it 1,000,000 years ago, extended ‘from a point a few degrees east of Iceland to about the site now occupied by Rio de Janeiro in South America. Embracing Texas and the Gulf of Mexico, the Southern and Eastern states of America, up to and including Labrador, it stretched across the ocean to our own islands, - Scotland and Ireland… embraced Brazil and the whole stretch of ocean across to the African Gold Coast.”
Bramwell described the people of Lemuria in detail and attributed them with being one of the “root-races of humanity.” According to Bramwell, Lemurians are the ascendants of the Altlanteans, who survived the period “of the general racial decadence which affected the Lemurians in the last stages of their evolution.” From “a select division of” the Atlanteans - after their promotion to decadence - Bramwell claims the Aryan race arose. “Lemurians, Atlanteans, and Aryans are root-races of humanity,” according to Bramwell.
In 1894, Frederick Spencer Oliver published A Dweller on Two Planets, which claimed that survivors from a sunken continent called Lemuria were living in or on Mount Shasta in northern California. The Lemurians lived in a complex of tunnels beneath the mountain and occasionally were seen walking the surface dressed in white robes.
This belief has been repeated by such individuals as the cultist Guy Warren Ballard in the 1930s who formed the I AM Foundation. It is also repeated by followers of the Ascended Masters and the Great White Brotherhood. This list includes such organizations as Bridge to Freedom, The Summit Lighthouse, Church Universal and Triumphant, The Temple of The Presence, and The Hearts Center.
Popular novels have also repeated the belief that Lemurians inhabit Mount Shasta. Among such novels, Vin Smith's The Outrageous Views of Professor Fogelman links Lemurians to Ancient Egypt, UFOs and a method of travel called vortex portals--essentially a pathway to sacred places on Earth as well as points unknown in the universe.
In Robert A. Heinlein's short story "Lost Legacy", three ordinary people rediscover innate human psychic abilities. They immediately come under attack from evil (but human) hidden elites, and are forced take refuge among a hidden colony of ancient masters in Mt. Shasta. Here they find that benevolent rebels of ancient times stored the secret history of humanity in Mt. Shasta and other mountains, to aid in humanity's eventual path to redemption. This history includes the rise and fall of the lost empire Mu, due to arrogance and the pursuit of power rather than enlightenment. The fall of Mu is said to have doomed humanity to the current 'Dark Age', in which the evil hidden elites forcefully maintain the ignorance of the masses.
Kumari Kandam is a legendary sunken kingdom sometimes compared with Lemuria (cf. works of G. Devaneyan, Tamil: ஞானமுத்தன் தேவநேயன்). According to these modernist interpretations of motifs in classical Tamil literature — the epics Cilappatikaram and Manimekalai that describe the submerged city of Puhar — the Dravidians originally came from land south of the present day coast of South India that became submerged by successive floods. There are various claims from Tamil authors that there was a large land mass connecting Australia and the present day Tamil Nadu coast.
Madame Blavatsky described the Lemurians (her third root race) as being colored black and described the Negroid race, the Dravidians and the Australoids, Papuans and Melanesians as being descended from them.
In the light of current day science, especially in marine archeology and anthropology, such postulates are seen as nothing more than fanciful imagination. One of the prime proponents of the Kumari Kandam theory, D. Pavanar clamied that the Tamils were a separate biological species known as "Homo Dravida". Such proclamations have confined the kumari kandam theory amongst fringe Tamil extremists with absolutely no scientific basis.
In reptilian conspiracy literature, a sunken Pacific continent (usually styled as Lemuria or Mu) is sometimes posited as the homeland of a reptilian race of creatures, often identified with dragons or nagas. Various bits of mythology and folklore are assembled in support, such as the Cambodian naga traditions. Folkloric claims of Australian aborigines sighting "dinosaur-like" creatures are also often viewed as evidence.
The earliest attestation of such notions in modern literature seems to have occurred in the works of H.P. Blavatsky, notably in The Secret Doctrine (1888), where she writes of "Dragon-men" who once had a mighty civilization on a Lemurian continent, until their rampant use of black magic brought about the end of their civilization, and their continent sank. Blavatsky in turn claims to have obtained this information from The Book of Dzyan. However, many consider that Blavatsky invented the book herself. Blavatsky believed that the terms "Dragon-men" or "Serpent-men" used to describe the Lemurian Lizard Beings in the Book of Dzyan were symbolic, intended to symbolize their advanced knowledge and magical powers.
Other occurrences of the idea seem to be in the Alley Oop (1932) comic-strip, and the Brazilian Piteco (1964), where lands named Moo (or "Mu") and Lem (adapted from Mu and Lemuria respectively) are presented as dinosaur-infested lands. This matched H. P. Lovecraft's descriptions of the city of R'lyeh in His Cthulhu Mythos.