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sciences that seek to study the earth and its neighbors in space
three types of renewable resources
A tentative explanation for a phenomenon which can be tested for validity
hypothesis has been extensively tested and has survived detailed scrutiny then the hypothesis can be promoted to the level of theory
- 1)Collection of scientific facts and
- 2)Development of individuals hypothesis
- or models.
- 3)Development of observations and
- experiments to test hypothesis.
- 4)Acceptance, modification or rejection
- of the hypothesis and models based on testing.
Evolution of the Earth: Two Hypothesis:
The Nebular Hypothesis (gas )
The Planetisimal Hyposthesis (part of the sun)
how old is the earth
4.5 billion or 4500 million years old
gases that envelope the earth
all living or once living materals
water on or near the earths surface
rocks and other inorganic mater that make up the earth service
Bulging at the equator and
flattened at the poles.
Equatorial diameter is
greator than the polar diameter
outer most layer of the earth
2 parts of the crust
contental (land) and oceanic ( ocean) crust
largest in volume and the middle part
broken into pieces that move in relationship with each other resulting in shfting contents valcano eruptions and new crust
plates move towards one another
plates move away for each other
plates slide by one another
cant be broken to other substances
smallest possilbe particle of an element. has all the properties of an element
earths chemical composits of the crust
largest oxygen(O) Silicon(Si) and Aluminum(AL)
atoms are aranged in 3dimensional orderly or regulary repeating
two most abundent elements in the crust
5 charistics of a mineral
- naturally occuring
- definite crystalline structure
8 properties of a mineral
Fundamental property. But cannot base the identification on it solely.
- More reliable than color. Obtained by rubbing the mineral on a piece of unglazed porcelain (called streak
- plate). Minerals that are metallic often leave a color on the plate
External Crystal Form:
External appearance of the mineral based on the internal arrangement of atoms.
Resistance of a mineral to scratching. Measured using the Mohs Scale of Hardness ranging from 1 (softest) (talc)to 10 (hardest).(diamond)
the mineral to break in smooth planes
breaks along a haphazard manner
weight of a mineral compared to a equal volume of water
- Smell: Clays have an earth smell.
- Taste: Halite tastes salty.
- Magnetite: Being attracted to a magnet.
- Striations: Plagioclase feldspar exhibits straight parallel lines on its surface.
Calcite minerals reacts with
naturally occuring consolidated materals comprising of minerals
relationship between rocks
formed from once molten material called magma
2 types of igneous rocks
Plutonic rocks are coarser grained (see the crystals) owing to slow cooling.
Volcanic rocks are fine grained (sometimes glassy) owing to rapid cooling.
(Intrusive-slow cooling) form below the surface of the earth. (e.g. granite).
Extrusive-fast cooling) form at or close to the surface of the earth (e.g. basalt).
(sudden chilling) volcanic glass (e.g. obsidian).
intermediate rate of cooling slow and fast (porphyrtic)
Based on texture and mineral composition.
- higher melting point
- less dence
- Rocks that have been formed from material derived from
- preexisting rocks
Some Characteristics of Sedimentary Rocks:
Lithification is when the sediments are transformed into rocks.
Clastic sedimentary rocks are the products of mechanical breakup of other rocks (e.g. conglomerate, sandstone, and shale).
Chemical sedimentary rocks are not from mechanical but forms via chemical precipitation or growth from solution (e.g. limestone).
Organic sediments consists of carbon rich remains of once living organism (e.g. coal).
more compression eaquals more
Rocks that have been formed under action of heat and/or pressure of preexisting rocks.
Some Characteristics of Metamorphic Rocks:
- Contact Metamorphisms: When heat is
- dominating agent (e.g. marble).
Regional Metamorphism: When pressure is the dominant factor (e.g. gneiss).
- Foliation: When the pressureon the rock is too great, then it will result in striations of the rock. With
- increasing pressure the banding becomes more prominent and goes from slate (low pressure)-phyllite, schist, and gneiss (high pressure).
The physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the earth’s surface..
The movement of rock and soil downslope under the action of gravity.
The removal of materials by agents such as wind, water, and ice.
Movement of eroded particles by wind, water, and ice
When transported material comes to rest
- The physical disintegration of the rocks. Breaks up the rocks but does not change the chemical
- composition. E.g., frost wedging, unloading, and biological activity.
- Decomposition of the rock by exposure to water and
- atmospheric gases. Changes the chemical composition and structure. E.g., oxidation, calcite dissolved when chemically weathered. Same effect observed for limestone and marble.
WEATHERING OF MINERALS
- The weathering of the minerals depends upon the composition of the mineral, as well as the
- internal arrangement of atoms. The weathering sequence is the same as that of the Bowen’s reaction
who is the bighest factor of erosion
- The chemical make up of the rock can establish how quickly a rock can weather. There are some minerals that weather faster in comparison to others. This is
- evident from comparing headstones. For
- instance, headstones made of granite are more resistant than marble ones.
Climatic factors such as temperature and moisture are instrumental in establishing the rate of weathering. For instance, regions with higher temperatures and precipitation will allow for chemical weathering to take place as opposed to colder and drier regions.
Different rates of weathering for different areas. Not all rocks weather uniformly. The weather depending on their composition as well the climatic conditions of the region they are located in.
Formed as a product of weathering.
- Layer of weathered material on top of the
- bedrock, consisting of unconsolidated
- pore spaces, mineral, and organic matter.
The soil texture refers to the proportions of different particle sizes.
(1941) mentioned that soils formed as a function of the following five factors:
Climate, Organic Matter, Relief, Parent Material, and Time (CLORPT).
- Soil Horizons:
- O-Horizon: Upper most layer. The organic horizon.
- A-Horizon: Dark colored soil. Contains humus.
- Also called the Zone of Loss/Leaching.
- B-Horizon: Accumulation of materials lost from A-Horizon. Also called the Zone of Gain.
- C-Horizon: Incompletely weathered parent material below the B-Horizon.
- R- Bedrock: Unexposed unweathered portion
- of the rock.
CONTROLS AND TRIGGERS OF MASS WASTING:
Gravity is the controlling force of mass wasting.
Role of Water
When saturated with water the material becomes heavy and more likely to move downslope. As the amount of water in the debris increases the rate of movement increases as well.
Stream undercutting a valley or waves hitting against the base of a cliff. This results in mass wasting as the gradient is steep. Angle of repose is the angle where material remains stable.
Removal of Vegetation:
Vegetation keeps the soil in place. Removal of vegetation increases the risk of mass wasting
Earthquakes as Triggers
Just an instigation for mass wasting to occur. Earthquake results in ground motion and shaking and this may disturb the material making it unstable and may result in mass wasting.