The Solid Earth! • The Earth is: • The third planet in our Solar System; • A terrestrial planet; • Composed of a rocky planet with a gaseous atmosphere
The study of the Earth is called Earth Science. Earth Science contains many disciplines including: a. atmospheric sciences b. geology (both physical & historical) c. hydrology d. oceanography e. meteorology & climatology f. astronomy
Earth’s History The Earth was formed at the same time as the other planets in our Solar System. The theory as to the formation of our planet is called the Nebular Hypothesis. This hypothesis says that our solar system evolved from an enormous rotating cloud called the solar nebula.
Nebular Hypothesis The nebula was composed mostly of hydrogen and helium. About 5 billion years ago, the nebula began to contract. It assumed a flat, disk shape with the protosun (pre-Sun) at the center.
More Nebular Hypothesis Next, the inner planets (terrestrial) begin to form from metallic and rocky clumps. Then, the larger outer (Jovian) planets began forming from fragments with a high percentage of ices.
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As Earth formed, the decay of radioactive elements and heat from high-velocity impacts caused the temperature of the Earth to increase. Denser materials coalesced or became concentrated toward the interior or core. Lighter rocky components floated outward…..toward the Earth’s surface.
Next, gaseous material escaped from Earth’s interior (through volcanoes) to produce the primitive atmosphere. The primitive atmosphere was made of methane, ammonia and carbon dioxide. There was NO free oxygen (O2) because it is too reactive.
The Earth is composed of many different spheres. The different spheres describe different parts of our Earth.
Hydrosphere • The hydrosphere contains: • All the water on the planet including the liquid water (oceans, lakes, rivers), the groundwater, the glaciers and ice caps, and the water found in the atmosphere.
Oceans The oceans are the largest part of the hydrosphere! They make up 71% of the Earth’s surface. 97% of the hydrosphere is found in the oceans. The oceans are marine or salt water.
Atmosphere! The atmosphere is the thin gaseous layer that surrounds our planet. It is comprised of 78% Nitrogen (N2), 21% oxygen (O2), 0-4% H2Ov, 1% argon (Ar), and .038% carbon dioxide (CO2)
The gases are held close to the Earth’s surface by gravity! The atmosphere is divided into layers: troposphere, stratosphere, mesosphere, thermosphere and then the exosphere.
Geosphere The geosphere is part of the Earth’s major spheres. The geosphere is made of the Earth’s interior, rocks/minerals, and landforms such as mountains.
The geosphere is made of four parts: • Crust (two types: oceanic and continental) • Mantle • Outer Core • Inner Core
Biosphere The biosphere is the area on Earth where life can possibly be found. It covers the upper geosphere, the hydrosphere, and the lower atmosphere.
The Solid Earth Let’s explore the Solid Earth’s layers in more detail!
Inner Core The inner core is the innermost layer of the Earth. The inner core is made of iron (80%) and nickel. It is extremely hot… about 5 000⁰ C.
The inner core extends from 6,360 km (the center of the earth) to 5,150 km (the bottom boundary of the outer core).
The existence of an inner core that is distinct from the liquid outer core was discovered in 1936 by seismologist Inge Lehmann using observations of earthquake-generated seismic waves that partly reflect from its boundary and can be detected by sensitive seismographs on the Earth's surface.
The outer core is the next layer of the Earth. The outer core mainly consists of iron and nickel and about 10% sulphur and oxygen.
The temperature in the outer core is about 4 500ºC. Because of this high temperature, the outer core is molten or liquid.
The outer core extends from 5,150 km (the boundary with the inner core) to 2, 890 km (the boundary with the mantle) below the earth's surface.
The liquid outer core spins (because of convection & the Earth’s rotation). The inner core does not spin because it is a solid. So the outer core spins around the inner core.