• Home /Exam Details (QP Included) / Main Exam / Optional Subject-Medical Group / Geology / Properties Of Rocks – Geology Notes – For W.B.C.S. Examination.
  • Properties Of Rocks – Geology Notes – For W.B.C.S. Examination.
    Posted on November 6th, 2019 in Geology
    Tags: , ,

    Properties Of Rocks – Geology Notes – For W.B.C.S. Examination.

    শিলার বৈশিষ্ট্য – ভূতত্ত্ব নোট – WBCS পরীক্ষা।

    Rock, in geology, naturally occurring and coherent aggregate of one or more minerals. Such aggregates constitute the basic unit of which the solid Earth is comprised and typically form recognizable and mappable volumes.Continue Reading Properties Of Rocks – Geology Notes – For W.B.C.S. Examination.

    Rocks are commonly divided into three major classes according to the processes that resulted in their formation. These classes are (1) igneous rocks, which have solidified from molten material called magma; (2) sedimentary rocks, those consisting of fragments derived from preexisting rocks or of materials precipitated from solutions; and (3) metamorphic rocks, which have been derived from either igneous or sedimentary rocks under conditions that caused changes in mineralogical composition, texture, and internal structure. These three classes, in turn, are subdivided into numerous groups and types on the basis of various factors, the most important of which are chemical, mineralogical, and textural attributes.

    General Considerations

    Rock types

    Igneous rocks are those that solidify from magma, a molten mixture of rock-forming minerals and usually volatiles such as gases and steam. Since their constituent minerals are crystallized from molten material, igneous rocks are formed at high temperatures. They originate from processes deep within the Earth—typically at depths of about 50 to 200 kilometres (30 to 120 miles)—in the mid- to lower-crust or in the upper mantle. Igneous rocks are subdivided into two categories: intrusive (emplaced in the crust), and extrusive (extruded onto the surface of the land or ocean bottom), in which case the cooling molten material is called lava.Sedimentary rocks are those that are deposited and lithified (compacted and cemented together) at the Earth’s surface, with the assistance of running water, wind, ice, or living organisms. Most are deposited from the land surface to the bottoms of lakes, rivers, and oceans. Sedimentary rocks are generally stratified—i.e., they have layering. Layers may be distinguished by differences in colour, particle size, type of cement, or internal arrangement.

    Metamorphic rocks are those formed by changes in preexisting rocks under the influence of high temperature, pressure, and chemically active solutions. The changes can be chemical (compositional) and physical (textural) in character. Metamorphic rocks are often formed by processes deep within the Earth that produce new minerals, textures, and crystal structures. The recrystallization that takes place does so essentially in the solid state, rather than by complete remelting, and can be aided by ductile deformation and the presence of interstitial fluids such as water. Metamorphism often produces apparent layering, or banding, because of the segregation of minerals into separate bands. Metamorphic processes can also occur at the Earth’s surface due to meteorite impact events and pyrometamorphism taking place near burning coal seams ignited by lightning strikes.

    Please subscribe here to get all future updates on this post/page/category/website

    Leave a Reply

    Your email address will not be published. Required fields are marked *

    This site uses Akismet to reduce spam. Learn how your comment data is processed.

     WBCS Foundation Course Classroom Online 2024 2025 WBCS Preliminary Exam Mock Test WBCS Main Exam Mock Test WBCS Main Language Bengali English Nepali Hindi Descriptive Paper