Earth Sicence Midterm

Geology

Physical Geology studies the materials and processes that compose and shape Earth. Historical Geology seeks to explain the origin and development of Earth over time.

Oceanography

The comprehensive study of oceans, including the study of the composition and movements of sea water, coastal processes, seafloor topography and marine life. 

Meteorology

The study of the atmosphere and the processes that produce weather and climate.

Astronomy

The study of the universe, including the exploration of how the Earth relates to all other objects in space.

Gradual Changes

Changes that aren’t visible to the naked eye

Ex: Plate Tectonics, Erosional Processes, Rock Formation

Rapid Changes

Destructive/rapid changes

Landslides, Volcanic Eruptions, Earthquakes

Open System

matter and energy is exchanged between the inside and outside of the system

Closed System

materials/energy are only exchanged within the system. The Earth is considered to be a closed system.

How many spheres the Earth has

4

Hydrosphere

A dynamic mass of water that is continually moving, evaporating from the oceans to the atmosphere, precipitating to the land and flowing back to the ocean.

Atmosphere

Earth is surrounded by a life-giving gaseous envelope, that is only a shallow layer around the solid earth.

Biosphere

Includes all life on Earth, most of which is concentrated near the surface.

Geosphere

Includes the solid Earth, from the surface to the center of the planet (a depth of 6400 km / 4000 miles!)

What’s the Nebular Hypothesis Theory

It says that the Sun and planets formed about 4.6 billion years ago from a giant cloud of gas and dust in space—called a solar nebula.

Steps of the Nebular Hypothesis Theory

1. A rotating cloud of gas and dust formed by an old supernova starts to collapse.

2. The nebula develops a center point of rotating material and flattens out into a disc.

3. Planetesimals form when chunks of small rocky material collide to form irregular shapes.

4. Planetesimals grow by increased gravitational pull that attract surrounding smaller rocks, gas and dust.

5. Protoplanets form as planetesimals collide and join together due to gravity. Protoplanets are more regularly shaped than planetesimals.

6. Planets form when gravity pulls material together more tightly.

Core

Composed of a dense, intensely hot mass of metal, which is mostly iron. It is subdivided into an inner core and outer core.

Inner Core

a solid despite the extreme temperatures, due to the extreme pressure conditions.

Outer Core

made up of molten iron and nickel. It separates the inner core from the rest of the solid Earth.

Mantle

Surrounds the molten outer core and is a hot, pliable layer of rock. This layer is composed of oxygen, silicon and magnesium. The depth of the mantle is approximately 2900 km.

Asthenosphere

Layer of the mantle located just below the lithosphere. It is much more fluid or viscous, and the lithosphere seems to "float" upon it.

The Lower Mantle

Extends from 660 kilometers to about 2,700 kilometers below Earth's surface. is hotter and denser than regions of the Lithosphere - Composed of the crust and upper most solid portion of mantle. It is considered the most rigid of the Earth’s layers.

Crust

topmost layer of the earth divided into two parts:

Continental crust

The crust located under land masses This region is thicker thick, up to 40 km in depth under mountains. Its composition is primarily granite.

Oceanic Crust

The crust located under the oceans. This region is thin, approximately 7 km. in depth and its composition is primarily dense basaltic rock

What are Earth Scientists

Geoscientists

Non-renewable Resources

Resources that cannot be replenished in a short period of time due to their fixed quantities (ie. fossil fuels, metals).

Renewable resources

Resources that can be replenished over short time periods (ie. energy from the sun, wind).

Minerals

building blocks of rocks

-Geologists define as any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation.

mineralogy

the study of minerals

Requirements for minerals

1.Naturally occurring

• Minerals form by natural geologic processes. Synthetic materials are produced in a laboratory or by human interaction, and they are not considered minerals.

2. Must be inorganic

   • When inorganic solids are buried and become part of the rock record, geologists consider them minerals (ex. Salt – halite)

3. Must be a solid

4. just have an orderly crystalline structure

   • Minerals are made up of atoms (or ions) that are arranged in an orderly, repetitive manner. This arrangement is reflected in regularly shaped objects called crystals.

5. It must have a definite chemical composition that allows for some variation

   • Most minerals are chemical compounds having compositions that can be expressed by a chemical formula.

   • The composition of some minerals vary within specific, well-defined limits because certain elements can be substituted for others of similar size without changing the mineral’s internal structure.

What charge are protons are

Positive

What charge are neutrons are

They have no charge

What charge are electrons are

negative

Cleavage

planes of weakness within their crystalline structure

element

A substance containing only one type of atom

Chemical Compounds

different atoms combine to form

Atomic Mass

Atomic mass is calculated by adding the number of neutrons and protons in an atom.

Physical Properties

The physical properties of minerals are determined by the structure and chemical composition of the minerals.

Mechanical Cohesion Properties

Properties in this category are derived from the strength of the chemical bonds that hold the mineral together. The major properties in this category are fracture, cleavage, hardness and tenacity.

Why does cleavage occur

when some atomic bonds are weaker than others in at least one direction. Because cleavages are controlled by both symmetry and structure, they are always along crystallographic planes and can be used to give guidance on the identity of a mineral specimen.

Indicator of cleavage

Cleavages occur along the weakest planes. When these planes are parallel, the mineral has cleavage.

Cleavages are often described by crystal forms. What is a crystal form?

a collection of identical crystal faces related by the point group symmetry of a mineral. The crystal itself is defined by the atomic structure of the mineral.

Crystal Face

Each smooth and flat surface on a crystal

Fracture

If a mineral breaks apart in haphazard ways – into fragments or rough pieces, then they do not have cleavage

Cleavage Vs fracture

Cleavage is the tendency of a mineral to break along flat, even surfaces, while fracture is the way a mineral breaks when it doesn't cleave, resulting in irregular or uneven surfaces

Hardness

whether a mineral can be scratched.

What scale is used to determine hardness

Mohs Scale of Hardness

(Lowest number means its the least hardest while the highest number is hard) Goes up to 1-10

Tenacity

the behavior of a mineral when it is deformed or broken.

There are 3 types

Brittle

type of tenacity

which mean the mineral breaks apart and powders easily

Malleable

Type of tenacity

which means that the mineral may be able to be pounded into sheets

ductile

Type of tenacity

which means that the mineral can be drawn into wire.

Optical Properties

Our visual perception of minerals is primarily dependent on the way that light strikes an object. Some of that light is absorbed and some is reflected. The balance between the two, impacts the way that we perceive the color and reflectivity of the surface.

Luster

how light reflects from a surface.

What are the classifications of luster and there meaning

Metallic (shiny) and Non-metallic (other forms)

vitreous

glassy luster

resinous

like smooth-surfaced plastic luster

dull/earthy

non-reflective luster

pearly

like a mollusk shell luster

adamantine

brilliant, like a diamond luster

Importance of color in minerals

certain wavelengths of light are absorbed, while others are reflected by the surfaces of the minerals

Streak

refers to the color of the mineral left behind when it is in powder form. The color of a mineral in powder form is usually much less variable, so it is a much more reliable property than color

what the thing used to observe streak

White or black small porcelain plates, called streak plates, are used to measure this property.

Double Refraction

There are some materials in which light enters the crystal and splits into two separate rays. As a result, when looking through a transparent mineral with this property, the surface beneath will appear doubled.

Mass-Dependent Properties

density and specific gravity.

Density

is defined as mass per unit volume. When studying minerals, expressed in units of grams per cubic centimeter (g/cm³).

Specific gravity

is defined as the density of a material divided by the density of water at 4ºC. The numerical values of specific gravity and density are essentially the same if the latter is expressed in units of grams per cubic centimeter, because the density of water at 4ºC is 1 g/cm³.

Heft

is a qualitative measurement technique of holding the specimen in the palm of your hand and gauging its general mass. The heavier objects typically with have a higher specific gravity. In our lab, we will use low (2.5-3.5 g/cm³), medium (3.5- 4.5 g/cm³) and high (greater than 4.5 g/cm³) heft to measure our samples.

Florescence

when they are put under Ultraviolet (UV) light. The short-wave radiation is absorbed by the mineral and radiated back as visible, longer wave radiation. Making them glow under these lights

Fluorite and calcite are two examples of minerals that fluoresce. 

Magnetism

Some minerals are attracted to magnets. For example, magnetite is strongly magnetic. 

Effervescence

bubbling or fizzing that takes place when dilute hydrochloric acid is applied to certain types of minerals. 

Odor and Taste

Some minerals, such as sulfur, have a very distinctive odor. Others have a distinct taste, such as halite (salty) or sylvite (bitter). Please NEVER taste samples in the laboratory setting

Silicates

-Largest mineral group (90% of Earth crust)

Basic Building Block for silicates

Silica Tetrahedra

Carbonates

Made up of cations

Cations

Positevely chared ions

Basic building structure for carbonate

Carbonate Structure

• 1 carbon + 3 oxygen

Halides

• Evaporites

• Easily dissolve in water

• Halogens bond to create halide minerals

Evaporites

Salt that form when salt water evaporates

Oxides

1 or 2 metallic elements

Phosphates

• Similar structure as Silica Tetrahedra but contains phosphorous rather than silicon

• Found in human bone

Sulfate

• Similar to silica tetrahedra but contains sulfur than silicon

• Similar to halides, form when salt water evaporates

Sulfides

• Form when metallic elements bond with sulfur without oxygen

• Commonly mistaken as sulfate

Rock Cycle

is a concept that is used to explain the formation and characteristics of the three basic rock types and how Earth’s natural processes, over long periods of time, change a rock from one form to another. Weathering and erosion and tectonic activity are among the processes responsible for the continued cycling of rocks from one form to another.

Igneous Rocks

form by the solidification/cooling of magma,

• molten rock beneath the Earth’s surface, or lava, above Earth’s surface. Magma and lava have a range of temperatures between 800ºC and 1200ºC on average.

intrusive, or plutonic rocks

When magma cools beneath Earth’s surface, the rocks that form are referred

Magma

Generated by melting rocks in the Earth’s mantle.

Lava

When magma reaches the surface.

felsic

refers to a set of minerals – feldspars, quartz and muscovite, and to a set of igneous rocks that have a composition dominated by these minerals.

what are igneous rocks primarily composed of

Igneous rocks are primarily composed of silicates but range from a composition that is light-toned, felsic, to very dark in color, ultramafic, based on the specific minerals that make them up.

Feldspar minerals

are the most common type of minerals in Earth’s crust, followed by quartz.

Ultramafic rocks

are mostly composed of ferromagnesium minerals (at least 90% mafic minerals)

• are associated with the upper mantle, rather than the crust, so they are only found in unusual locations where a sliver of oceanic crust has been faulted onto continental crust, in xenoliths, or where mountain ranges have formed after an ocean basic has been closed through subduction.

Intermediate rocks

are those that have roughly equal percentages of felsic and mafic silicates.

plutonic (intrusive) igneous rock

forms by the cooling of magma intruded within the Earth’s crust. These types of rocks cool very slowly, resulting in large, well-formed crystals.

A volcanic (extrusive) igneous rock

forms from extruded lava much more quickly than intrusive igneous rock. As a result, these rocks have many small crystals, that are often not visible to the observer

quenching

When extrusive rock cools extremely quickly, they may not form crystals at all.

Coarse-Grained (Phaneritic) igneous rocks

have crystals that are easily visible, and they are all roughly the same size throughout. Coarse-grained igneous rocks form beneath Earth’s surface, so they are intrusive (plutonic) rocks.

Granite

Type of Coarse-Grained (Phaneritic) igneous rocks

-This felsic, intrusive igneous rock is predominantly white, pink, or gray in color. They mainly consist of feldspar, quartz, mica and amphibole minerals.

Gabbro

Type of Coarse-Grained (Phaneritic) igneous rocks

• This mafic, intrusive igneous rock is usually black or dark green in color. They mainly consist of minerals like plagioclase and augite. They are very common in deep oceanic crust.

Diorite

Type of Coarse-Grained (Phaneritic) igneous rocks

• This intermediate, intrusive igneous rock is a 50/50 split of dark and light-colored minerals. The primary minerals found in this rock are feldspar, biotite, hornblende and/or pyroxene.

Fine-Grained (Aphanitic) igneous rocks

formed above Earth’s surface. Typically, individual crystals are unable to be seen with the naked eye and may require the use of a hand lens for observation.