Earth Science – Second Quarter study guide
Weather Fronts and Storms
 Air mass – a huge block of air with similar temperature and humidity throughout.
 They form when global winds are light and air sits over the same area for a while.
 They are named by where they form because that affects their temperature and
humidity:
 Maritime – formed over the ocean  moist/humid.
 Continental – formed over the land  dry
 Tropical – formed near the equator  warm.
 Polar – formed near the poles  cold.
 Air masses affect the weather by bringing their humid/dry, warm/cold air to our area.
 Cold air is more tightly packed  denser, but warm air expands making it less dense.
That means the denser cold air will push the less dense warm air up and out of the way.
 Fronts are where air masses meet.
 Clouds and storms often occur at fronts because that’s where the warm, humid air and the
cold, dew point temperatures meet.
 Cold fronts – cold air mass pushing (just bulldozes warm air mass out of the way).
Intense, brief storms occur right along the front followed by cooler temperatures.
 Warm fronts – warm air mass pushing (rides up over the back of denser cold air mass).
Front extends for many miles ahead, clouds gradually lower as front gets closer, usually
slow moving, can cause long periods of precipitation.
 High and Low Pressure Systems – Large regions of high or low air pressure that cause
the air to move. These systems affect weather and can create and move fronts.
 High Pressure systems – Air sinks slowly in a clockwise spiral. Clear skies and gentle
breeze.
 Low Pressure systems – Air rises rapidly in a counter clockwise spiral. Cloudy, stormy
weather.
 Hurricanes – Large, tropical, rotating, low pressure systems with wind speeds of 74 mph
or more.
 They form in the ocean when abnormally warm ocean water creates a low-pressure
region. The Coriolis effect makes them spin.
 In the U.S., hurricanes affect the Gulf and Atlantic coasts.
 Effects including storm surge, high winds and flooding making them extremely
damaging and dangerous.
 Climate – the expected weather in a place during each season based on a history of
observations.
 Sand (or any rocky material of the land) heats fast and cools fast. Water (like the oceans)
heats slow and cools slow (meaning it holds its heat for a long time).
 Climate Factors (things that determine an area’s climate).
 Latitude (warmer closer to equator and colder closer to the poles)
 Altitude (gets colder as you go higher)
 Distance to ocean (the ocean changes temperature slowly; cooler summers, warmer
winters).
 Ocean current (warm or cold water flowing in a steady pattern in the ocean).
 Microclimate – a small area that has a different climate than its surroundings – like the
shady ground behind a pine tree.
 Rain Shadow – as humid air moves from the ocean and goes over a mountain range, it
cools, causing more precipitation falls on the ocean side of the mountains than on the
back side of the mountains. The dry side is said to be in the rain shadow.
 Climate Change.
 Ash from volcanic eruptions can block sunlight and lower temperatures.
 Ice Ages – periods of global cooling where glaciers covered much of the land.
 El Niño – weak trade winds leave moist air in Pacific near North America. Wetter &
warmer weather is likely.
 Global warming. Increased greenhouse effect causes earth’s average temperatures to
rise.
 Humans are contributing by burning fossil fuels.
 Those effects can occur much faster than natural way – living things may not have
time to adapt.
 Effects include rising sea levels, heat related health problems, endangering wildlife
and agricultural problems.
Geology – the study of planet earth.
Rocks and Minerals
 Minerals are naturally occurring, solid, have a crystal structure and definite chemical
composition.
 Minerals can be identified by hardness (scratch test), streak (color of mark left on streak
plate), density (D=M/V), color, luster (metallic, glassy, dull, etc.), cleavage, fracture and
special properties (magnetic, fizzes in acid, taste, etc.).
 You should be able to do the tests and identify a mineral sample.
 Rocks are mixtures of minerals.
 3 main rock types:
 Igneous – formed from molten rock (“mineral soup”) of volcanic activity.
 Rock formed below the surface is intrusive, above the surface is extrusive.
 Crystals form in the magma (below ground) and lava (above ground) as they cool.
 Slow cooling means bigger crystals, so intrusive rocks have bigger crystals.
 Sedimentary – formed from layers of rock particles (shale, sandstone, conglomerate),
plants (coal), or shells (limestone) becoming packed and cemented together (by
minerals in the ground water).
 Wind and water cause the erosion necessary for sedimentary rocks to form.
 Metamorphic – formed when existing rock is put under extreme heat (near a magma
chamber) and pressure (when mountains are formed or being buried deep
underground). Often shows layering (foliation) like pages in a book or in light and dark
stripes.
 You should be able to identify the different rock types:
 Igneous has crystals in a “freckled” pattern or gas bubbles.
 Sedimentary has sediment (pieces of rock or shells), often one color, possibly fossils in
it.
 Metamorphic has crystals but in a layered (foliated) pattern. Often dark but shiny or
alternating light and dark stripes.
 Rock cycle – rocks are not destroyed, they change from one type to another as forces
(like heat, pressure, melting, volcanic activity and erosion) act on them.