Chapter 6 Flashcards
Which is the most abundant gas in Earth’s atmosphere?
nitrogen
What is the ratio of nitrogen to oxygen in Earth’s atmosphere?
4 parts nitrogen to 1 part oxygen
The major constituents of Earth’s atmosphere are
77% nitrogen and 21% oxygen.
The atmosphere that we are now breathing is the _____ atmosphere Earth has had
third
Why did Earth’s earliest atmosphere, composed primarily of hydrogen and helium, not last long?
Hydrogen and helium are light gases, and they soon escaped into space.
What were the dominant gases in Earth’s second atmosphere?
carbon dioxide and nitrogen
Billions of years ago, Earth’s atmosphere was composed primarily of carbon dioxide. What happened to much of this carbon dioxide?
dissolved into Earth’s oceans
Earth’s atmosphere differs from those of near-neighbor planets Venus and Mars in one important respect:
Earth’s atmosphere has a significant fraction of oxygen
Photosynthesis in plants on Earth maintains a balance between which of the two atmospheric gases?
oxygen and carbon dioxide
The presence of oxygen in Earth’s atmosphere is thought to result directly from what type of process?
activity biological of plants and animals
Ozone in the stratosphere performs an important task that protects life on Earth. What is it?
Ozone absorbs much of the dangerous solar ultraviolet light.
An “ozone hole” is
a region of the stratosphere above the South Pole where ozone levels occasionally drop to very low levels.
Which of the following terms does NOT label a region of Earth’s atmosphere or near-Earth environment?
chromosphere
In which layer of Earth’s atmosphere is the ozone layer located?
stratosphere
Ozone is a gas consisting of
molecules containing three oxygen atoms.
Why does the temperature in the stratosphere increase with increasing altitude?
The stratosphere is heated by solar ultraviolet radiation absorbed by the ozone layer.
What is the basic structure of Earth’s atmosphere?
four layers of alternating temperature profiles: temperature decreasing, then increasing, then decreasing, then increasing with altitude
The lowest temperature in Earth’s atmosphere is about
200 K
In which layer of Earth’s atmosphere does weather occur?
troposphere
Earth’s magnetic field is most probably generated by
electric currents in Earth’s electricity-conducting molten core.
Earth’s magnetosphere is the
region beyond Earth’s atmosphere where Earth’s magnetic field protects us from the solar wind.
What causes the phenomenon of the aurora?
Charged particles from the magnetosphere strike atoms in the upper atmosphere, causing them to emit characteristic colors of light.
The names we use for the Moon’s maria were
invented a few hundred years ago after the first telescopic observations of the Moon.
Craters are not apparent on Earth at the present time in the abundance seen on the Moon because
plate tectonics has returned cratered surface layers into Earth’s interior, and weathering has obliterated the more recent craters.
Most of the craters on the Moon were formed by
bombardment by interplanetary meteoritic material.
Why do the larger craters on the Moon have central peaks?
The crater floor rebounded upward after the initial compression from the impact of an interplanetary rock.
Maria are
ancient lava floodplains.
Major maria on the Moon exist
only on the Earth-facing side.
What is the name of a long, winding crack in a lunar mare?
rille
The mountain ranges on the Moon are
the walls of craters caused by impacts of large objects early in the geological history of the Moon.
What are spring tides?
high tides that are significantly higher than the average high tide
Spring tides occur
twice a month, at full and new Moon.
When do neap tides occur?
whenever the Earth-Moon line makes a 90° angle to the Earth-Sun line
