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Extraterrestrial life forms: Calvin encounters many extraterrestrial life-forms in the course of the strip, usually during adventures as his alter-ego, Spaceman Spiff. Most of these aliens are non-humanoid, bizarre monsters, but represent Calvin's imaginative perception of Susie, his parents, and teachers.
Engraving from William Smith's monograph on identifying strata based on fossils. Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment.
In the study of rock and sediment strata, geologists have recognized a number of different types of strata, including bed, flow, band, and key bed. [1] [5] A bed is a single stratum that is lithologically distinguishable from other layers above and below it. In the classification hierarchy of sedimentary lithostratigraphic units, a bed is the ...
William 'Strata' Smith (23 March 1769 – 28 August 1839) was an English geologist, credited with creating the first detailed, nationwide geological map of any country. [1] At the time his map was first published he was overlooked by the scientific community; his relatively humble education and family connections prevented him from mixing ...
The principles of lithostratigraphy were first established by the Danish naturalist, Nicolas Steno, in his 1669 Dissertationis prodromus. [1] A lithostratigraphic unit conforms to the law of superposition, which in its modern form states that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks. [2]
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The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields pertaining to geological stratigraphy.In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface to form new deposits over time.
Transitional forms are seen as falling between the various groups in terms of anatomy, having a mixture of characteristics from inside and outside the newly branched clade. [ 7 ] With the establishment of cladistics in the 1990s, relationships commonly came to be expressed in cladograms that illustrate the branching of the evolutionary lineages ...