This ppt tells us about the Igneous rocks. Igneous rocks are rocks formed from molten magma. The material is made liquid by the heat inside the Earth's mantle.
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2. •Amongst the common rock forming minerals Felspathoid minerals containing less % of silica are also present which are usually allied with Feldspars Nepheline (Silicate of sodium and aluminium=>Albite Leucite (Silicate of potassium and aluminium=>Orthoclase
3. James Hutton (1727–1797), the eminent 18th century gentleman farmer and founder of modern geosciences, authored the concept of the rock cycle, which depicts the inter-relationships between igneous, sedimentary, and metamorphic
4. PETROLOGY •Is a branch of geology, which deals with study of rocks (Petro=rock, ROCKS SEDIMENTARY IGNEOUS METAMORPHIC -thin veener above the Sial -most abundant -proportion is similar to and Sima in Oceanic -primary rocks that of Igneous rocks and Continental -source is magma or -change of forms of Ig. Crusts lava And Sed. Due to -secondary rocks Temprature, Pressure and Chemical Fluids
5. Importance of petrology in civil Engg. • It provides an opportunity to interpret the physical properties of individual rocks, likewise: texture, structure, mineral composition, chemical composition etc. • This helps in knowing the strength, durability, colour, appearance, workability etc. • These properties are very important for CE to know because different rocks are suitable for different purposes and no rock is ideal or best suited for all purpose.
6. Granite: hard, competent, durable => suitable for foundation Limestone: comparatively soft=> best for flooring Marble: soft and attractive=> flooring/sculpturing etc. Sandstone: sculpturing, wall etc.
7. VOLCANO: A gap in the Earth’s Crust where molten rocks and other material escape onto the Earth’s surface IGNEOUS ROCKS: The rocks formed through volcanic action OR The rocks which are derived from a molten mass “magma or lava” SOURCE OF IGNEOUS ROCKS: Magma: Molten mass comprising most abundant elements in earth – Si, Al, Fe, Ca, Mg, K, H & O. Where the SiO2 is most abundant amongst all. Temperature of Magma- 10400 to 12000 C
8. Influencing Factors for Magma Flow and Formation of Igneous Rocks • Overlying sedimentary rocks as overburden plays important role in formation of igneous bodies eg: dykes, sills, laccoliths, bysmaliths, phacoliths, lopolith, volcanic necks, batholiths and chonoliths. • The beddings in the sedimentary rocks facilitates the magma to move through or intrude/inject through the weak planes
9. KINDS OF IGNEOUS ROCK
10. FLUIDITY OF MAGMA Fluidity or Viscosity of magma depends on content (%) of Silica Silica Rich Silica poor -known as Acidic magma -Known as Basic magma -More viscous, so do not -Less viscous, moves spreads and piles up at one faster and occupies place larger area However, the viscosity of magma is considerably influenced by temperature too. When temperature is less-more viscous and when High temperature- less viscous.
11. BROAD CLASSIFICATION OF IGNEOUS ROCKS Volcanic rocks Intermediate rocks Plutonic rocks (Extrusive rocks) (Hypabyssal rocks) (Intrusive -Lava or Magma rocks) flows -dykes, sills, -Pyroclastic flows batholiths, laccoliths etc. Name comes from Greek god of the underworld - Pluto
12. FORMS OF VOLCANIC ROCKS Extrusive (volcanic) igneous rocks form when molten rock erupts from Earth's interior through a volcano or fissure and cools rapidly at the surface in form of Lava and hence it does not have any specific shape Lava flows: On eruption lava simply flows on the surface and on the basis of surface appearance, lava flows are described as blocky lava and ropy lava
13. Block Lava: is less mobile i.e. more viscous and has a Rough and irregular surface. Vesicles are few and irregular in shape When cools down it result into angular, chunky texture. This causes the lava to thicken and to break apart as the flow continues to move down slope. Such a texture is referred to as a-a, probably because of the pain inflicted on a person trying to walk across such a flow.
14. Ropy Lava: is more mobile i.e. less viscous, it has a wrinkled but smooth and shiny surface on Vesicles are more in number, small- spherical in shape.
15. PYROCLASTS OR PYROCLASTIC: Extrusive igneous rock texture referred to as pyroclastic. This texture results from a very explosive eruption, which sends not only lava flying through the air, but also fragments of the volcano itself. All airborne volcanic fragments, referred to as pyroclasts
16. •The rock fragments thrown out during volcanic eruption are called •Based of shape and size they are categorized Pyroclasts come in many sizes: the smallest are called ash, slightly larger are lapilli, and the biggest are called blocks or ash lapilli
17. A large pyroclasts are known as volcanic bombs. Typical shape with head and a tail. Bombs can result into severe damage if they strike.
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