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Slate can be made into roofing slate, a type of roof tile which are installed by a slater. Slate has two lines of breakability—cleavage and grain—which make it possible to split the stone into thin sheets. When broken, slate retains a natural appearance while remaining relatively flat and easy to stack.
A less severe cold period or ice age is shown during the Jurassic-Cretaceous (150 Ma). There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
An artist's impression of the last glacial period at glacial maximum [4]. The LGP is often colloquially referred to as the "last ice age", though the term ice age is not strictly defined, and on a longer geological perspective, the last few million years could be termed a single ice age given the continual presence of ice sheets near both poles.
Phyllite Photomicrograph of thin section of phyllite (in cross polarised light) Fractured Duke stone showing phyllitic texture Phyllite. Phyllite (/ ˈ f ɪ l aɪ t / FIL-yte) is a type of foliated metamorphic rock formed from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation. [1]
The Huronian glaciation (or Makganyene glaciation) [1] was a period where at least three ice ages occurred during the deposition of the Huronian Supergroup. Deposition of this largely sedimentary succession extended from approximately 2.5 to 2.2 billion years ago (), during the Siderian and Rhyacian periods of the Paleoproterozoic era.
A long-quiet yet massive super volcano, dubbed the "Long Valley Caldera," has the potential to unleash a fiery hell across the planet, and the magma-filled mountain has a history of doing so.
To geologists, an ice age is defined by the presence of large amounts of land-based ice. Prior to the Quaternary glaciation, land-based ice formed during at least four earlier geologic periods: the late Paleozoic (360–260 Ma), Andean-Saharan (450–420 Ma), Cryogenian (720–635 Ma) and Huronian (2,400–2,100 Ma).
The formation was originally designated as the Hondo Slate by Evan Just in his 1937 survey of pegmatites in northern New Mexico. [5] However, this name conflicted with other unit names, and it was renamed the Pilar Phyllite Member of the Ortega Formation by Arthur Montgomery in 1953 [6] Bauer and Williams promoted it to formation rank within the Vadito Group in their sweeping revision of the ...