4. Batuan Dan Mineral 2g5s4c

Earth Materials Minerals •A mineral is a naturally occurring substance with characteristic physical and chemical properties. •Nearly all rocks are composed of minerals. •Polymineralic rocks are composed of more than one mineral, ex. granite. •Monomineralic rocks are composed of only one mineral, ex. limestone.

Earth Materials Mineral Composition Minerals are composed of elements. Some minerals contain only one element (copper, sulfur and graphite (carbon)). •Most minerals are made up of only a few elements. •Oxygen is the most common element by weight and volume. •Silicon is second most abundant by weight.

Earth Materials Properties of Minerals Characteristics of minerals include: •color •hardness •luster/cahaya/kilauan •streak/garis/coreng •cleavage/pecah/potongan and fracture/patah/retak •density

Earth Materials Properties of Minerals Differences in properties are used to categorize and identify minerals. •The acid test is the use of hydrochloric acid on limestone. The result is that bubbles of CO2 are liberated/dilepaskan. •Minerals have a characteristic crystalline structure, in many cases the silicon-oxygen tetrahedron.

Rock Formation The Rock Cycle relates the three types of rocks.

Earth Materials The Rock Cycle •Any one rock type can change into any other rock type. •There is no preferred direction of movement of materials in the rock cycle for any one mass of material. •There is no exact point of separation between the rock types.

Earth Materials The Rock Cycle •Sedimentary rocks often contain sediments or fragments which have varied origins. •The composition of some rocks suggests that the materials (sediments or minerals) in the rock have undergone multiple transformations (changes) within the rock cycle.

Weathering and Erosion Weathering is the breakdown of rocks to form particles called sediment. •Physical weathering is the breakdown of rock without chemical changes –Freezing and thawing (frost action) –Thermal expansion and contraction

•Chemical weathering is the breakdown of rock by chemical action –oxidation, hydration, solution by acids

Weathering and Erosion Factors affecting weathering are: •Exposure--more exposure means faster weathering •Particle size--the smaller the particles, the greater the surface area •Mineral composition--some minerals (quartz) are more resistant to weathering than others (mica and feldspar) •Climate--warmth and moisture enhance weathering

Weathering and Erosion Soil Soil is a product of weathering. •Residual soil forms from the weathering of rocks nearby. •Transported soil is brought in by erosion. Soil layers develop over time. The soil composition generally tends to reflect the composition of the rocks below.

Weathering and Erosion Soil Profiles •A soil horizon is a vertical layer of soil with certain characteristics. For example, the top layer of soil usually is rich in organic material. •Lower horizons result from weathering. The horizon just above the bedrock will contain partially weathered rock. •There is a subsoil layer just below the topsoil layer.

Weathering and Erosion Soil types •Residual soil is formed from the rocks below the soil layer. These soils usually relate to the underlying rocks. They can be sandy, clayey or loamy/tanah liat organik if they have much organic material. •Transported soil is one that has been move into an area from someplace else by erosion.

Weathering and Erosion Erosion Erosion is the process by which sediments are obtained and transported. •Transporting agents include water (streams), glaciers, waves, density currents in water, wind, and people. •Driving forces include gravity and change of potential to kinetic energy.

Weathering and Erosion Stream/aliran Erosion Stream water carries sediments. •Dissolved minerals are carried in solution. •Small solid particles are carried in suspension. •Large solid particles are moved by rolling or bouncing along on the bottom of the stream.

Weathering and Erosion Stream Erosion The ability to carry sediment depends on velocity. The velocity depends on the gradient (slope) and discharge (volume) of the stream. •Stream velocity varies. On a curve, it is fast on the outside and slow on the inside.

Weathering and Erosion Stream Erosion

Weathering and Erosion Wind Erosion •Wind causes erosion. When wind carries sediment, it forms dunes/bukit pasir.

Glacial erosion •A glacier can carry large amounts of dirt/kotoran. •When the glacier stops moving, it drops the dirt forming a moraine/bagian depan sungai es yang bergerak maju.

Weathering and Erosion Glacial Erosion An example is the Hubbard Glacier in Alaska

Weathering and Erosion Glacial Erosion •There is a moraine in New Jersey left over from the last ice age. The glacier also formed Long Island.

Deposition Deposition is also known as sedimentation. Deposition occurs when the velocity of water, wind or other erosional system decreases. Deposition depends on: •Particle size--heavier particles sediment faster •Shape--spherical particles sediment faster •Density--denser particles sediment faster

Deposition Rock layers are formed by sediments. The size of the particles determines the rock type. Boulders, gravel, pebbles/batu kerikil-conglomerate Sand--sandstone Silt--siltstone Colloids, clay—shale/serpih Colloids, chemical sediments--limestone

Deposition Deposition by moving water

Deposition Deposition by moving water •When a river enters the ocean, the velocity decreases. •Sediments are deposited and form a delta. •An example is the Mississippi River Delta.

Rock Formation Rocks are the solid material that make up the Earth. There are three types: •Sedimentary Rocks--formed by solid sediments weathered from pre-existing rocks •Igneous Rocks--formed by cooling of liquid rock •Metamorphic Rocks--formed by transformation of igneous or sedimentary rocks by reheating

Rock Formation Formation of sedimentary rocks •Cementation--larger particles are cemented by minerals precipitated out of the water •Compression--very small particles are compressed by immense weight of water and sediment layers about them •Chemical action--ionic materials precipitate out of the water •Biological processes--precipitation of minerals by biological organisms

Rock Formation Properties of sedimentary rocks •Particles of sedimentary rocks resemble the sediments they came from •Some contain a mixture of sediments, others a single type of sediment •Some sedimentary rocks are of organic origin (example: coal) •Sedimentary rocks form layers called strata •Sedimentary rocks frequently contain fossils

Sedimentary Rocks Identifying sedimentary rocks

• There are three major groups of sedimentary rocks. • Detrital rocks form from sediments washed in by water, such as gravel, sand and mud. • Chemical sedimentary rocks have crystalline texture: limestone, dolostone, gypsum, salt • Biochemical sedimentary rocks: clastic (limestone from shells), chert, coal

Igneous Rocks Properties of igneous rocks

• Igneous rocks are nonsedimentary in origin • They form by solidification or crystallization of liquid rock under the Earth called magma • Longer cooling time causes big crystals in the rock. Shorter cooling time causes small crystals in the rock. • Texture of igneous rock depends on the size of the crystals.

Igneous Rocks Types of igneous rocks

Igneous rocks form a gradation between two extremes. • Felsic rocks are high in Al and Si. • Mafic rocks are high in Mg and Fe. Generally, igneous rocks are identified on the basis of crystal size (texture) and mineral composition

Igneous Rocks Sequence of cooling of silicate minerals-Bowen’s Reaction Series • Bowen’s reaction series s for the crystallization of intermediate and felsic magmas from an original basaltic (mafic) magma. It has two branches, continuous and discontinuous.

• In the continuous branch, calcium-rich plagioclase feldspar crystallizes first followed by sodium-rich plagioclase feldspar.

Igneous Rocks Sequence of cooling of silicate minerals-Bowen’s Reaction Series • In the discontinuous branch there is a series of one mineral changing to another over time as the melt cools. • The sequence is: olivine --> pyroxene --> amphibole --> biotite mica.

• At this point the two sequences finish with: potassium feldspar (orthoclase) --> muscovite mica --> quartz.

Igneous Rocks Importance of texture and composition The texture of igneous rocks depends on the size of the crystals as well as their arrangement. Rocks with large crystals cooled slowly. Those with small crystals cooled faster. Mafic rocks are denser and darker than felsic rocks (ex: pyroxene, olivine). Felsic rocks are lighter in color and denser (ex: quartz, felspar, mica)

Metamorphic Rocks Properties of metamorphic rocks

• Metamorphic rocks are also nonsedimentary in origin. • Metamorphism is a response to heat and pressure within the Earth’s crust. • Such conditions result from plate collisions, mountain building and sometimes localized heating such as with volcanic eruptions.

Metamorphic Rocks Properties of metamorphic rocks

• Metamorphic rocks form from recrystallization of pre-existing rocks. • Metamorphic rocks often show banding where like crystals are arranged in layers. • They have a distorted structure caused by curving and folding of the bands.

Metamorphic Rocks Foliated vs nonfoliated metamorphic rocks

• Foliated rocks have crystals arranged in parallel planes. Examples are slate, schist, gneiss. • Nonfoliated rocks do not have a preferred orientation among their minerals. Examples are marble, quartzite, greenstone.

Metamorphic Rocks Steps leading to the formation of gneiss

• Most gneiss begins with recrystallization of clay-rich sedimentary rocks during regional metamorphism. • Gneisses are composed mainly of quartz and/or feldspar, which cause the light bands.

• The dark bands come from biotite and hornblende.

Metamorphic Rocks Origin and composition of marble

Marble is a metamorphic rock that was originally limestone or dolomite. Limestone marble is made of CaCO3. Dolomite marble is made of CaMg(CO3)2. Limestone marble reacts with the acid test. Dolomitic marble also reacts with the acid test but it must be powered first.

Metamorphic Rocks Regional metamorphism

• Regional metamorphism occurs over a wide area and results from tremendous temperatures, pressures and deformation conditions deep under the surface. • It results in a gradation from from low to high metamorphism depending on the levels of temperature and pressure involved.

Civilization and Earth Materials Humans use fossil fuels for the major part of their energy needs. These include coal, oil and natural gas. Minerals are used in a variety of human activities. Rocks are quarried and used as building stones and pavement. Earth resources are not renewable. They cannot be restored easily in your lifetime.

Landscape development Landscapes are the features of the surface of the Earth. Features include: • slope of the land • shape of surface features • stream drainage patterns

• stream slope • soil characteristics

Landscape development Measuring Landscape Characteristics

• Measurements can be made using actual observations, maps, aerial photographs or satellite images. • Gradients, slopes and profiles are given on topological maps.

• Major types are mountains, plateaus and plains

Landscape development Forces that produce landscapes

• Uplift is a rai of a region of land caused by forces in the crust or by tectonic interaction. • Leveling forces break down rocks and transport material on the Earth’s surface. These include weathering, erosion, deposition, subsidence.

Landscape development Forces that produce landscapes

• Erosion is the removal of weathered rock materials from their source area. • Mass wasting is the downslope movement of rocks, sediments, or soil under the influence of gravity.

Landscape development Factors that influence landscape development • Climate affects the rate of change of a landscape. • Glaciers produce U-shaped valleys and deposit soil with a wide range of particle sizes. • Streams may not flow all the time in arid climates. Some arid regions have internal drainage where streams deposit water into a basin rather than leading to the ocean. The Great Salt Lake is an example.

Landscape development U-shaped valley caused by a glacier

Landscape development Factors that influence landscape development • Bedrock greatly influences the landscape above it. • Different types of rock have different degrees of resistance to weathering and erosion. • Stream drainage patterns indicate information regarding the contour of the bedrock below.

Landscape development Human influence on landscape development • Removal of forests for development leads to accelerated erosion of soil when it rains. • Acid rain causes increased chemical weathering of rocks. Example: accelerated erosion of limestone. • Environmental conservation can help conserve limited natural resources.

Landscape development Geologic features can be represented by photographs, as well as topographic and geological maps. Maps are interpreted using scales and colors to represent features. Topographic maps indicate locations of equal altitude using contour lines.

Geologic maps use colors and symbols to represent rock ages and structures.

Landscape development On a topographic map, the steepness of a slope is indicated by the nearness of the contour lines.

A very steep slope has contour lines very close together. A long, gradual slope has contour lines far apart. Direction on a contour map is indicated by an arrow pointing north. Distances are given by a distance scale.

Natural Hazards People live in risky places. A flood plain can fill up with water and carry away the work of generations. Seismic hazards are issues near faults, such as the San Andreas Fault. It is not a good idea to live on the slopes of a volcano, lest it erupt. People live near Mt. Etna, anyhow.