Download Composition of Earth Outline: • Earth`s Stats and internal structure

Composition of Earth
Outline:
• Earth’s Stats and internal structure
– Chemical v. Physical Properties
• Mohorovičić discontinuity=“Moho”
• Composition of Minerals
The Earth’s Stats
heterogeneous in composition
3rd planet from sun
93,000,000 miles from sun
Diameter ~8,000 miles
Circumference ~25,000 miles
Mass 5.9x1021 tons
(5,900,000,000,000,000,000,000 tons)
Composition of Continental Crust, Weight percent
Oxygen (O)
46.6%
Silicon (Si)
27.7%
Aluminum (Al)
8.1%
Iron (Fe)
5%
Magnesium (Mg)
2.1%
Calcium (Ca)
3.6%
Potassium (K)
2.6%
Sodium (Na)
2.8%
All others
<1.5%
O + Si= 74.3%
Composition of Whole Earth, Weight percent
Iron (Fe)
35%
Oxygen (O)
30%
Silicon (Si)
15%
Magnesium (Mg)
13%
Nickel (Ni)
2.4%
Sulfur (S)
1.9%
Calcium (Ca)
1.1%
Aluminum (Al)
1.1%
All others
<1%
Earth’s Internal Structure
Layers defined by composition (P-waves vs. S-wave and the Earth’s Interior)
1. Crust
Continental-30-50 km thick, thickest beneath mts.; mostly granitic
Oceanic- 7 km thick; basalt
Base is defined by abrupt change in seismic characteristics of rx
2. Mantle
3. Core
Earth’s Interior by waves
Mohorovičić discontinuity=“Moho”
Mantle shows increase in velocity to depths
70 km below ocean
120 km below continents
Sudden decrease may be due to partial melting
Low velocity separates:
Lithosphere=crust and uppermost mantle
Asthenosphere=mantle below low velocity zone
2900 km=abrupt increase in velocity
Layers of the Earth by Physical Properties
1. Lithosphere
– Upper most top of Mantle
– Includes crust (less dense than rocks beneath)
e.g., Continental and Oceanic
Oceanic thinner than Continental
1. Asthenosphere
– Hot, slowly flowing, weak rock
– Near top of mantle/beneath lithosphere
– Plastic (solid, but jello-like)
2. Mesosphere (Mantle)
– Solid
– Rocks=mostly iron, magnesium silicates
– Moho marks boundary between mantle, crust
3. Core
– Outer-liquid, mostly iron
– Inner-solid, comp sim. to outer
Composition of minerals and matter
•Elements
•Basic building blocks of minerals
•100+ are known (92 naturally occurring)
•Periodic Table
•Atoms
•Smallest particles of matter
•Retains all the characteristics of element
•Atomic structure
•Central region = nucleus
•Consists of protons (positive charges), neutrons (neutral charges)
•Electrons
–Negatively charged particles that surround nucleus
–Located in discrete energy levels called shells
•Formation of compound by combining two or more elements
•Ionic bonding
•Atoms gain or lose outermost (valence) electrons to form ions
•Ionic compounds consist of orderly arrangement of oppositely charged
ions
•Covalent bonding
•Atoms share electrons to achieve electrical neutrality
•Covalent compounds are generally stronger than ionic bonds
•Van der Waals or Molecular bonding
•Usually strong covalent bonds with weaker electro-statically charged
layers between.
•Metallic bonding
•Valence electrons are free to migrate among atoms
•Weaker and less common than ionic or covalent bonds