Fundamentals of Soil Science SOL 114 PDF

Fundamentals of Soil Science SOL 114 Prepared by _ Jancy Garg Rocks and Minerals Prepared by _ Jancy Garg Unit -1 Prepared by _ Jancy Garg What are Rocks? *Rocks a...

Fundamentals of Soil Science SOL 114 Prepared by _ Jancy Garg Rocks and Minerals Prepared by _ Jancy Garg Unit -1 Prepared by _ Jancy Garg What are Rocks? *Rocks are the materials that form the essential part of the Earth’s solid crust. “ *“Rocks are hard mass of mineral matter comprising one or more rock forming minerals”. Prepared by _ Jancy Garg *Rocks are formed from the molten material known as magma. The study Prepared by _of rocks Jancy Garg is called Petrology (in Greek, petra means rock, logos means science). Petrology deals with the description of rocks; *petrogenesis is the study of the origin of rocks. Prepared by _ Jancy Garg Formation of rocks 1. Cooling and consolidation of molten magma within or on the surface of earth = Igneous or Primary rocks 2. Transportation and cementation of primary rocks = Sedimentary or Secondary Prepared by _ Jancy Garg rocks 3. Prepared Alteration of the by _ Jancy existing primary and secondary rocks = Metamorphic rocks Garg Prepared by _ Jancy Garg MCQ Which statement is not correct? A- The study of the origin of rocks called petrology. B- Rocks are hard mass of mineral matter Prepared by _ Jancy Garg C- Rocks are formed from the molten material known as magma D-All above Prepared by _ Jancy Garg E- none Prepared by _ Jancy Garg  Formation of rocks Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg  Soil forming rocks and Classification On the basis of their genesis and structure, rocks are generally grouped into 3 classes: Igneous Sedimentary and Prepared by _ Jancy Garg Metamorphic The composition of the upper 5 km of the Earth’s Crust is as follows: Prepared by _ Jancy Garg ❖Sedimentary rocks (74%) ❖Igneous rocks (18%) ❖Other rocks (8%) Prepared by _ Jancy Garg Classification of Rocks Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg  Cooling and consolidation of molten magma within or on the surface of earth results A-Metamorphic rocks B-Sedimentary rocks C- Igneous or Primary rocks. D- none Prepared by _ Jancy Garg Transportation and cementation of primary rocks results. A-Sedimentary Prepared or Secondary rocks by _ Jancy Garg B-Metamorphic rocks C- Igneous or Primary rocks D-none Prepared by _ Jancy Garg 1. Igneous rocks (primary or massive rocks) These are first formed in the earth crust due to the solidification of molten magma on or beneath the surface of the earth. Based on the mode of formation, they are further classified as extrusive and intrusive rocks. Extrusive rocks or volcanic rocks Prepared by _ Jancy These rocks are formed due to the consolidation Garg of magma on the surface of the earth. The magma, when it flows on the Earth surface is called LAVA. E.g. Basalt. Intrusive rocks or plutonic rocks Prepared by _ Jancy Garg These rocks are produced due to solidification of magma below the surface of the earth. Plutonic – intrusive rocks solidifies at greater depth and Hypabassal rocks solidifies at shallow depth from the surface. E.g. Granite, syenite, diorite, Gabbro etc. Rocks formed in vertical cracks are called dykes and in horizontal cracks are called sills. Prepared by _ Jancy Garg Vesicular rocks: Molten magma cools on the surface. Steam of water is entrapped into rocks and forms vesicles. 2. Igneous rocks Classification Based on the silica content , rocks are also classified as 1. Acid rocks : >65% SiO2 (Granite, Rhyolite) 2. Intermediate : 56 to 65% SiO2 Prepared by _ Jancy Garg (Sub acid rocks 60 to 65% SiO2 (Syenite and Trachyte) (Sub basic rocks 56 to 60 % SiO2 (Diorite and Andesite) Prepared by _ Jancy Garg 3. Basic rocks : 40 to 55% (Gabbro, basalt) Prepared by _ Jancy Garg MCQ Which rock is present in highest proportion in the composition of the upper 5 km of the Earth’s Crust ? A-Sedimentary rocks B-Igneous rocks Prepared by _ Jancy Garg C-Other rocks D-None Prepared by _ Jancy Garg Prepared by _ Jancy Garg https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/GabbroRockCreek1.jpg/220px-GabbroRockCreek1.jpg Prepared by _ Jancy Garg Prepared by _ Jancy Garg Gabbro Prepared by _ Jancy Garg  2. Sedimentary rocks These rocks are formed from the consolidation of sediments accumulated through wind or water action at the surface of the earth. Many are deposited in layer or formed through chemical reactions as precipitates from aqueous solutions. Sediments may contain various size particles cemented together by substances like SiO2, Fe2O3 or lime. These rocks are also called as clastic rocks. Classification of sedimentary rocks Based on origin, sedimentary rocks are classified in to different groups Residual:- When the products of weathering Prepared settle at by _ Jancy Garg that place where they have been formed, they form in to hard mass Ex:- Bauxite Mechanical or Detrietal :- Weathered fragments are transported , deposited in beds of varying thickness and cemented. Ex: Sand Prepared by Stone, _ Jancy Shale, Garg Conglomerate Inorganic or Chemically Formed :- These are formed by evaporation or precipitation of material in sea or lake water Formed through evaporation: - Halite (Rock salt) , Gypsum Formed through precipitation and flocculation: - Lime stone, Dolomite Prepared by _ Jancy Garg Formation of Sedimentary rocks:- Four stages are recognized in the formation of sedimentary rocks. Weathering:- The igneous rocks (Primary rocks) disintegrate owing to physical, chemical and biological weathering and provide basic materials for the formation of sedimentary rocks. Transportation:- The disintegrated material is transported by the agencies, such as water, wind, glaciers, runoff andPrepared gravity.byTransportation _ Jancy Garg is a function of speed of water Deposition or Sedimentation: The materials comprising minerals and rock fragments are deposited when the carrying agent has no longer energy enough to Prepared by _ Jancy Garg move it further. Coarser particles settle first and the finer particles later. This kind of deposition is called ‘graded bedding’ Digenesis:- It refers to the transformation of unconsolidated sediments to hard rock. It involves compaction and cementation. Prepared by _ Jancy Garg  Sedimentary sandstone with iron oxide bands https://upload.wikimedia.org/wikipedia/commons/thumb/6/61/SandstoneUSGOV.jpg/220px-SandstoneUSGOV.jpg Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg 3. Metamorphic rocks The word ‘metamorphic’ means “change in form” Metamorphosis is used as a general term for all those changes that alter more or less completely the original characters of rock. FORMATION: Igneous and sedimentary rocksPrepared subjected to tremendous by _ Jancy Garg pressures and high temperatures, It causes to metamorphism. The changes in the deeply buried rocks are brought about by the combined action of internal heat and pressure. The structure Prepared and by _ Jancy Gargmineralogical composition of metamorphic rocks depend on the composition of original rock and the kind of metamorphism. The banded or laminated character is the most peculiar feature of metamorphic rocks. Prepared by _ Jancy Garg 3. Metamorphic rocks Changes brought about by chemically activated waters - Hydro- metamorphism Ex: Sand stone to Quartzite; Granite or Basalt to Laterite. Changes brought about by Heat - Thermo-metamorphism Ex: Limestone to crystalline marble Prepared by _ Jancy Garg Changes brought about by Pressure - Dynamo -metamorphism Ex: Granite - Granite-gneiss (Partial foliation) Gneiss - Schist (Complete Prepared byShale foliation); _ Jancy Garg - Slate Changes brought about by Heat & Pressure - Dynamo-thermal metamorphism Ex: crystalline gneisses, schists and marbles are formed. Prepared by _ Jancy Garg Classification of Metamorphic rocks Based on the texture and structure of minerals, the metamorphic rocks are divided in to three groups Foliated (Parallel structure) (Leaved or leafy): These rocks contain micas and ferro- magnesian minerals and show foliation as the minerals are flattened and arranged in parallel layers. Prepared by _ Jancy Garg Ex: Gneiss, Schist (Coarse grained); Phyllite (medium grained); Slate (Very fine grained) Unfoliated (massive structure): These rocks contain quartz and feldspars and do not show Preparedeven foliation by _ Jancy under Garg pressure because of large sized crystals. Ex: Talc-schist, amphibolite and graphite. Granular: These consisting of mostly equidimensional grains. Ex: Quartzite, Marble Prepared by _ Jancy Garg  Granite---------------Gneiss Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg  Gneiss-------------Schist Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg  Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg  Sedimentary rocks are formed from the molten material known as A- magma B-Schist C-Granite D-None The study of rocks is called as by _ Jancy Garg Prepared A-Pedology. B- Rock science PreparedC-byPetrology _ Jancy Garg D- none Prepared by _ Jancy Garg  Prepared by _ Jancy Garg Prepared by _ Jancy Garg Prepared by _ Jancy Garg