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Chapter 1Planets in our Solar System differ radically from one another in both size and composition. The inner planets
(Mercury, Venus, Earth, and Mars), the ones closer to the Sun, are relatively small. We call them the terrestrial
planets, because like the Earth, they consist of a shell of rock surrounding a ball of metal. The outer planets (Jupiter,
Saturn, Uranus, and Neptune) are known as the giant planets, jovian planets. Celestial objects = naturally occruing
bodies in the universe.
The overall composition of giant planets differs markedly from that of terrestrial planets. Specifically, most of the
matter in Jupiter and Saturn consists of hydrogen and helium as a gas, liquid, or as a strange liquid-metal state.
Because so little solid material occurs in these planets, astronomers refer to them as gas giants. In contrast, most of
the matter in Neptune and Uranus consists of water, carbon dioxide, and methane that has been frozen into solid
ice, we call these planets ice giants.
The universe contains two basic entities: matter (what makes up an abject) and energy (the inherent ability of a
region of space and matter within it to do ‘work’. The amount of matter: mass.
Gravity is the attractive force that one mass exerts on another. 1 stadium = 0,1572 km. If the source of waves moves
toward you experience a higher frequency and shorter wavelength then if it were to move away from you (blue shift,
towards and red shift, away(light)), this is called the doppler effect. The light coming to the earth from distant
galaxies appears red, thus they must be moving away from us. If all the galaxies are moving away from us the
universe must be expanding.
According to the big bang theory, all matter and energy was initially packed into an infinitesimally small point called
a singularity, which exploded. How the earth was formed (pg34-35).
Early on earth was homogenous inside. When the temperature got hot enough, iron began to melt. The iron
accumulated at the centre of the planet to form a metallic core.
In addition to planets, the Solar System contains a great variety of other objects:
Moons: A moon is a solid object, of detectable size, that orbits a planet.
Asteroids: An asteroid is a relatively small rocky or metallic object that orbits the Sun.
Kuiper Belt and Oort Cloud Objects: About a trillion bodies of ice, with diameters ranging from less than 1 cm to
2,000 km, lie outside the orbit of Neptune.
Dwarf Planets: Asteroids and Kuiper Belt objects with a diameter greater than about 900 km are known as dwarf
planets.
Comets: Kuiper Belt or Oort Cloud objects that follow elliptical orbits that bring them into the inner Solar System are
called comets.
1
, Chapter 5
A MINERAL is a naturally occurring, solid, crystalline material formed by geologic processes, which has a definable
chemical composition.
- Formed by geologic processes: Geologists now consider solid, crystalline materials produced by organisms
to be minerals, too. To avoid confusion, the term biogenic mineral may be used when discussing such
materials.
- Solid: Matter in the solid state can maintain its shape indefinitely, so it will not conform to the shape of its
container. Minerals cannot be liquids (such as oil or water) or gases (such as air).
- Crystalline material: In a crystalline material, the atoms reside in an orderly, fixed pattern, locked in place by
chemical bond. The three-dimensional geometric arrangement of atoms or ions that defines that pattern is
called a crystal structure.
- Definable chemical composition: This phrase simply means that it’s possible to write a chemical formula for
a mineral. For example, quartz has the formula SiO2—it contains the elements silicon and oxygen in the
proportion of one silicon atom for every two oxygen atoms.
- Inorganic: To understand the meaning of inorganic, we must first understand what we mean by organic.
Organic chemicals consist of molecules that (1) include carbon-carbon and/or carbon-hydrogen bonds and
(2) either form in living organisms or have structures like those of chemicals that form in living organisms.
Almost all minerals are inorganic, in that they are not organic chemicals. But we have to add the qualifier
“almost all” because mineralogists now consider a few dozen organic substances formed by “the action of
geologic processes on organic materials” to be minerals. Examples include the crystals that grow in ancient
deposits of bat guano.
A crystal is a single continuous piece of crystalline material bounded by flat surfaces, called crystal faces, that form
naturally as the crystal grows. When light shines through a crystal, diffraction occurs. Different crystal structures of
the same chemical composition are called polymorphs of a material.
There are 5 ways for a crystal to form:
1. Freezing
2. precipitation from a water solution
3. biomineralization
4. diffusion
5. precipitation from gas.
If a crystal grows uninhibited into an open space it displays well-formed crystal faces, a euhedral crystal (i.e. crystals
in a geode). Minerals without well-formed crystal faces, are called anhedral grains.
Mineral formation (pg130-131).
Minerals have different properties to recognise them by, like: Color, streak(color of powder), Luster(how surface
scatters light), hardness(mohs hardness scale), specific gravity(density compared to water), crystal habit(shape of
faces), special properties, fracture and cleavage(the way they break).
Mineral classes:
• Silicates (SiO44-) 95% of the continental crust. • Halides (halogens)
Tetrahedron shaped. Silicon-Oxygen • Carbonates CO32-)
tetrahedron. • Native metals
• Sulfides (S2-) • Sulfates (SO42-)
• Oxides
Rocks of the oceanic crust and of the Earth’s mantle consist almost entirely of silicates, so silicates are the most
common minerals on the Earth. As noted earlier, silicates contain the SiO44− anionic group, We refer to this anionic
group as the silicon-oxygen tetrahedron.
2
,Mineralogists distinguish among several groups of silicate minerals, detailed below, based on the arrangement of
silica tetrahedra. The arrangement, in turn, determines the degree to which tetrahedra share oxygen atoms.
- Independent tetrahedra: In this group, tetrahedra are independent and do not share any oxygen atoms. The
attraction between the tetrahedra and positive ions holds crystals together. This group includes olivine, a
glassy green mineral, and garnet.
- Single chains: In a single-chain silicate, tetrahedra link to form a chain by sharing two oxygen atoms. The
most common of the many different types of single-chain silicates are pyroxenes.
- Double chains: In a double-chain silicate, tetrahedra link to form a double chain by sharing two or three
oxygen atoms. Amphiboles are the most common minerals in this group.
- Sheet silicates: Tetrahedra in this group share three oxygen atoms and therefore link to form two-
dimensional sheets. Other ions fit between the sheets in sheet silicates. Because of their structure, sheet
silicates have a single strong cleavage direction, and they occur in “books” of very thin sheets. In this group,
we find micas and clays. Clays occur only in extremely tiny flakes.
- Framework silicates: In a framework silicate, each tetrahedron shares all four oxygen atoms with its
neighbors, forming a three-dimensional structure. Examples include feldspar and quartz. Plagioclase, which
tends to be white, and orthoclase (also called potassium feldspar, or K-feldspar), which tends to be pink,
represent the two most common feldspars. Feldspars contain aluminum, which substitutes for silicon in the
tetrahedra, as well as varying proportions of other elements, such as calcium, sodium, and potassium.
Quartz, in contrast, contains only silicon and oxygen; the ratio of silicon to oxygen in quartz is 1:2, so the
mineral has the familiar formula SiO2 (Fig. 5.17b).
3
, Interlude B
Sediment consists of loose fragment of rocks or minerals broken off bedrock, mineral crystals that precipitate
directly out of water, and shells or shell fragments. Sediment is produced by weathering, the physical and chemical
breakdown of pre-existing rock at or near the earth’s surface. Regolith = any loose material that covers bedrock at
the earth’s surface.
Physical weathering: mechanical weathering, breaks intact rock into unconnected clasts.
• Jointing – natural cracks formed due to removal of overburden or to cooling.
• Frost wedging – when water in a crack freezes it forces the crack open and may cause it to grow
• Salt wedging – dissolved salt in water precipitates and forms crystals in open pore spaces in rocks. The
growing crystals push apart the surrounding grains and weaken the rock, so when exposed to wind and rain
the rock disintegrates into separate grains.
• Root wedging – Tree roots that grow into joints can force them open
• Thermal expansion – immense heat can bake a rock > the outer layer of the rock expands, when cooled in
contracts. This change of force makes the outer part fall off.
• Animal attack
Chemical weathering: chemical reactions that alter or destroy minerals when rock comes in contact with water
solutions or air.
• Dissolution – minerals in water separate into ions that become surrounded by water molecules
• Hydrolysis - water chemically reacts with minerals and form other minerals
• Oxidation – a reaction during which an element loses electrons > commonly takes place when elements
combine with oxygen
• Hydration - the absorption of water into the crystal structure of minerals cause them to expand which
weakens the rock
Tectonic processes raise the land surface above the sea level. Once exposed, rock interacts with air and water and
undergoes chemical and physical weathering, ultimately breaking down to produce sediment. Convection in the
atmosphere generates wind, rain and snow. Flowing water, ice, and air erode and transport sediment to sites of
deposition. Leaching by downward-percolating rainwater, along with the addition of organic material, produces soil.
In a general sense, soil consists of rock or sediment that has been modified by physical and chemical interaction with
organic material and rainwater, over time, to produce a substrate that can support the growth of plants.
Three processes taking place at or just below the surface of the Earth contribute to soil formation.
1. Production of mineral debris: Chemical and physical weathering produces loose debris, new mineral grains
(such as clay), and ions in solution from sediment or bedrock.
2. Interaction with water: water percolates down through the debris and carries dissolved ions and clay flakes
→ new mineral crystals precipitate out of the downward-percolating water or form by reaction of the water
with debris → the water leaves behind its load of fine clay.
The region in which new minerals grow and clay collects is the zone of accumulation. We refer to the region
in which this downward transport occurs as the zone of leaching.
3. Interaction with organisms: The microbes, fungi, plants, and animals in soil absorb nutrient atoms, leave
behind organic waste, produce acids that weather mineral grains, and also physically churn and break up the
soil. When organisms die, they rot and transform into organic carbon that mixes with the mineral debris of
soil. The accumulation of rotted organic debris makes up humus.
Because different soil-forming processes operate at different depths, soils typically develop distinct zones, known as
soil horizons, arranged in a vertical sequence called a soil profile.
- the O-horizon (the prefix stands for organic), consists almost entirely of organic matter and contains barely
any mineral matter.
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