-
Earth Science
sciences that seek to study the earth and its neighbors in space
-
three types of renewable resources
-
Hypothesis:
A tentative explanation for a phenomenon which can be tested for validity
-
Theory
hypothesis has been extensively tested and has survived detailed scrutiny then the hypothesis can be promoted to the level of theory
-
Scientific Methods
- 1)Collection of scientific facts and
- measurements.
- 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
-
atmosphere
gases that envelope the earth
-
biosphere
all living or once living materals
-
hydrosphere
water on or near the earths surface
-
geosphere
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
-
crust
outer most layer of the earth
-
2 parts of the crust
contental (land) and oceanic ( ocean) crust
-
mantel
largest in volume and the middle part
-
-
plate tectonics
broken into pieces that move in relationship with each other resulting in shfting contents valcano eruptions and new crust
-
convergent
plates move towards one another
-
divergent
plates move away for each other
-
transform
plates slide by one another
-
elements
cant be broken to other substances
-
atoms
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)
-
crystallinity
atoms are aranged in 3dimensional orderly or regulary repeating
-
silicon-oxygen tetrahedron
two most abundent elements in the crust
-
5 charistics of a mineral
- naturally occuring
- solid
- definite
- definite crystalline structure
-
8 properties of a mineral
-
Color
Fundamental property. But cannot base the identification on it solely.
-
Streak:
- 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.
-
Hardness
Resistance of a mineral to scratching. Measured using the Mohs Scale of Hardness ranging from 1 (softest) (talc)to 10 (hardest).(diamond)
-
Cleavage
the mineral to break in smooth planes
-
fracture
breaks along a haphazard manner
-
specific gravity
weight of a mineral compared to a equal volume of water
-
Special Properties:
- 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.
-
Chemical Tests:
Calcite minerals reacts with
hydrochloric acid
-
-
rock
naturally occuring consolidated materals comprising of minerals
-
rock cycle
relationship between rocks
-
IGNEOUS 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.
-
Characteristics of
Igneous Rocks:
-
plutonic
(Intrusive-slow cooling) form below the surface of the earth. (e.g. granite).
-
valcanic
Extrusive-fast cooling) form at or close to the surface of the earth (e.g. basalt).
-
natural glass
(sudden chilling) volcanic glass (e.g. obsidian).
-
Porphyry
intermediate rate of cooling slow and fast (porphyrtic)
-
IDENTIFICATION OF
IGNEOUS ROCKS:
Based on texture and mineral composition.
-
darker rocks
ligher color
- higher melting point
- less dence
-
Sedimentary Rocks
- 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
carbon
-
Metamorphic Rocks:
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).
-
Weathering
The physical breakdown (disintegration) and chemical alteration (decomposition) of rocks at or near the earth’s surface..
-
Mass wasting
The movement of rock and soil downslope under the action of gravity.
-
Erosion
The removal of materials by agents such as wind, water, and ice.
-
Transportation
Movement of eroded particles by wind, water, and ice
-
Deposition
When transported material comes to rest
-
Mechanical Weathering
- 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.
-
Chemical Weathering
- 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.
-
CHEMICAL
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
- series.
-
who is the bighest factor of erosion
we are
-
Rock Characteristics
- 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.
-
Climate
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.
-
Differential Weathering:
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.
-
SOILS
Formed as a product of weathering.
- Layer of weathered material on top of the
- bedrock, consisting of unconsolidated
- pore spaces, mineral, and organic matter.
-
Soil Texture:
The soil texture refers to the proportions of different particle sizes.
-
Factors Affecting
Soil Formation:
Jenny
(1941) mentioned that soils formed as a function of the following five factors:
Climate, Organic Matter, Relief, Parent Material, and Time (CLORPT).
-
soil horizons
- 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.
-
Oversteepened Slopes:
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.
|
|