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THE GEOSPHERE. The geosphere. Is made up of rocks and rocks are made up of minerals Minerals are the building blocks of rocks Elements are the building blocks of minerals. The geosphere is made up of rocks and minerals. Just eight elements account for 98% of Earth’s mass.
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The geosphere • Is made up of rocks and rocks are made up of minerals • Minerals are the building blocks of rocks • Elements are the building blocks of minerals
The geosphere is made up of rocks and minerals • Just eight elements account for 98% of Earth’s mass.
FORMATION OF THE GEOSPHERE • Formation of the elements by the collision of the Sun • Released of heat (change from kinetic energy to heat energy) • More gravitational attraction toward the planet`s center • Radioactive decay
Earth`s layers • Core: iron rich, dense • Mantle: less dense, rocky • Crust: even less dense, rocky. Composed of lighter elements (Oxygen and Silicon)
Earth`s crust Oxygen and silicon make up 75% of Earth’s crust.
Minerals • Is a naturally formed, inorganic crystalline solid, composed of a determinable and ordered arrangement of atoms with specific chemical composition • It is not manufactured in laboratories • Ordered in a geometric pattern • Have a range of compositions • It is not made up of organic compounds (no Carbon involved neither living things)
Mineral properties • Are classified by the chemical composition and the crystal structure • Identified by physical properties
Crystal form • Perfect geometric forms • Is an expression of the ordely arrangement of its atoms • Every mineral has a unique combination of composition and crystal form
Crystal form • Some minerals have the same composition but different arrangement of their atoms • Diamond and graphite are two examples • Such minerals are called polymorphs. With a different crystal structure, the minerals will have different properties.
Crystal form • Internal atomic arrangement is determined by atom/ion charge, size, and packing. • The conditions in which the crystal grows also affect crystal form. • Temperature, pressure, space for growth
Mineral Properties: Hardness • Hardness is the resistance of a mineral to scratching. • Hardness is dependent on the strength of a mineral’s chemical bonds. • Bond strength is determined by ionic charge, atom (or ion) size, and packing. • The Mohs Scale compares the hardness of different minerals.
Mineral Properties: Cleavage and Fracture Cleavage is the property of a mineral to break along planes of weakness. • Planes of weakness are determined by crystal structure and bond strength.
Mineral Properties: fracture Fracture occurs in minerals where bond strength is generally the same in all directions. • Minerals that fracture do not exhibit cleavage.
Mineral Properties: Color • Color is an obvious feature for many minerals, but it is not reliable for mineral identification. • Chemical impurities can change a mineral’s color. • A mineral may occur in many color variations or be colorless.
Mineral Properties: Density Density is the ratio of a mineral’s mass to its volume. In simple terms, it is how heavy a mineral feels for its size (volume).
Classification of Rock-Forming Minerals There are two classifications of minerals: • Silicate minerals • Nonsilicate minerals Silicate minerals make up more than 90% of the Earth’s crust.
Classification of Rock-Forming Minerals Silicate minerals are made up of silicon (Si) and oxygen (O) atoms, along with other elements (Al, Mg, Fe, Mn, and Ti).
Classification of Rock-Forming Minerals The Silicates are divided into two groups: • Ferromagnesian silicates • Contain iron and/or magnesium • Tend to have high density and are darkly colored • Nonferromagnesian silicates • No iron or magnesium • Tend to have low density and are light in color
Classification of Rock-Forming Minerals Nonsilicate minerals make up about 8% of Earth’s crust. • Carbonate minerals • Calcite, dolomite • Oxide minerals • Ore minerals—hematite, magnetite, chromite • Sulfide minerals • Ore minerals—pyrite, galena
Classification of Rock-Forming Minerals • Sulfate minerals • Gypsum, anhydrate • Native elements • Gold, platinum, iron
The Formation of Minerals and Rock Minerals form by the process of crystallization. Crystallization is the formation and growth of a solid from a liquid or gas Minerals crystallize from two primary sources: • Magma (molten rock) • Water solutions
The Formation of Minerals and Rock Minerals crystallize systematically based on their respective melting points. • The first minerals to crystallize from a magma are those with the highest melting point and the lowest amount of silica. • The last minerals to crystallize from a magma are those with lower melting points and higher amounts of silica.
The Formation of Minerals and Rock Water solutions associated with later stages of crystallization from magma account for many important deposits. • As water solutions become chemically saturated, minerals precipitate • For chemical sediments, solubility rather than melting point determines which minerals will form first • Low-solubility minerals precipitate first. • High-solubility minerals precipitate last.
Rock Types A rock is an aggregate of minerals—a physical mixture. The three categories of rock reflect how they were formed: • Igneous Formed from cooling and crystallization of magma or lava
Rock Types • Sedimentary Formed from preexisting rocks subjected to weathering and erosion
Rock Types • Metamorphic Formed from preexisting rock transformed by heat, pressure, or chemical fluids
Igneous rocks • Igneous rocks are formed from the cooling and crystallization of magma or lava. • Role of heat: induce melting points • Role of pressure: reduced pressure lowers the melting temperature of rock • Role of fluids: fluids (primarily water) cause rocks to melt at lower temperatures.
Sedimentary rocks Sedimentary rocks are products of 4 processes: • Weathering • Erosion • Deposition • Sedimentation
Sedimentary rocks • Weathering—the physical breakdown and chemical alteration of rock at Earth’s surface • Two types of weathering: • Mechanical weathering—breaking and disintegration of rocks into smaller pieces. • Chemical weathering—chemical decomposition and transformation of rock into one or more new compounds.
Sedimentary rocks • Erosion—the physical removal of material by mobile agents such as water, wind, ice, or gravity. • Erosion does not occur in place. It involves movement.
Sedimentary rocks • Deposition: the stage in which eroded particles come to rest. Larger particles are the first to be deposited. Smaller particles are able to remain with the flow. In this way, sediments are sorted according to size as they are deposited.
Sedimentary rocks • During sedimentation, sediment particles are deposited horizontally layer by layer. • As deposited sediment accumulates, it changes into sedimentary rock.
Metamorphic Rocks • Metamorphic rocks are produced from: • Igneous rocks • Sedimentary rocks • Other metamorphic rocks • Metamorphism occurs via recrystallization and mechanical deformation.
The rock cycle • Molten rock rises from the depths of Earth, cools, solidifies, and eventually returns to become magma again.
