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Astronomy Ch. 6 - Earth
Terms in this set (35)
Why is Earth not a perfect sphere?
because of inertia and Earth's spinning motion
Earth's layers separated when Earth was heated to what state? What is this process called?
What elements make up over 72% of the earth?
oxygen and silicone
What are silicates?
oxygen and silicone
What heated Earth?
What do we monitor when studying Earth's interior?
What are S waves?
they move material perpendicular to the wave direction of travel and only move through solids
What are P waves?
they compress material and travel easily through liquid or solid
What is a radioactive element? What does it produce when it decays?
potassium; calcium and argon
What is convection?
- heat generated by radioactive decay in the Earth that creates movement of rock
- occurs because hotter material will be less dense than its cooler surroundings and consequently will rise while cooler material sinks
- cause of earthquakes, volcanoes, Earth's magnetic field, and the atmosphere
What is rifting?
- the crust stretches, spreads, and breaks the surface
- occurs when the plates spread apart
What is subduction?
- one piece of crust slips under the other
When the continents were connected millions of years ago, what was it called?
What is the atmosphere mainly made of?
oxygen and nitrogen
What compounds did Earth's first atmosphere have more of? What split them apart?
carbon dioxide, water, ozone, and argon; UV radiation from the sun
Most of the hydrogen was lost to what? Why?
solar UV; it was so intense
What protects us from deadly UV radiation?
a layer of ozone
What is the greenhouse effect? How is it helpful? What will happen if it increases too much?
the trapping of infrared in the atmosphere; it makes the surface hotter; the temperature will rise, causing ice to melt, resulting in higher sea and ocean levels, and more frequent extreme weather
What protects our atmosphere?
What are Van Allen radiation belts?
a layer of energetic charged particles that is held in place around a magnetized planet by the planet's magnetic field
What forms the aurora?
solar particles interacting with the magnetic field
What is the Coriolis Effect? What does it cause?
the apparent curved motion, in the absence of any force an object will move in a curved path over a rotating object; it causes jet streams, the spiral pattern of large storms as well as their direction of rotation, the trade winds that move from east to west in 2 bands, the deflection of ocean currents creating flows such as the Gulf Stream
What is precession? How long is 1 cycle? What will this, along with Earth's elliptical orbit effect over time?
Earth's wobble on its axis; about 26,000 years; Earth's climate
What is density?
mass for a given volume
About how old is the Earth?
4-4.5 billion years old
What is the most common element?
What is the density of water, surface rocks, iron, and Earth?
1 g/cm^3; 3 g/cm^3; 8 g/cm^3; 5.5 g/cm^3
What are the layers of the Earth?
crust- solid, low-density, thin, made of many silicates
mantle- hot, thick, not-quite liquid
outer core- liquid, mixture of iron, nickel, and perhaps sulfur
inner core- solid, iron and nickel
Why is Earth's core solid?
it is under so much pressure
What is the estimated temperature of the Earth's core? What are the likely causes of this high temperature?
6500 K; gravitation - compression and radioactive decay
What are plate tectonics?
the shifting of large blocks of the Earth's surface
What are magnetic fields?
- how magnetic forces are communicated
- have polarity (direction)
- generated either by large-scale currents or currents on an atomic scale
Origin of the Earth's magnetic field
- generated by currents
- caused by rotational motion and convection
- geographic poles and magnetic poles do not coincide
- both the position and strength of the poles change slightly from year to year, even reversing their polarity every 10,000 years or so
What is aurora
- charged solar particles stream past Earth, they generate electrical currents in the upper atmosphere
- currents collide with and excite molecules
- as the molecules de-excite, light photons are given off resulting in aurora
What is the magnetosphere?
the region of the Earth's environment where the Earth's magnetic field affects particle motion
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