Earth Science Unit
Review Summary
The Earth/Sun/Moon System
The Earth rotates (spins) on its axis in a counterclockwise direction. A single rotation takes one day (24
hours). This is the reason that we have a period of daylight and a period of darkness in NY every “day.”
The direction of rotation is what makes the sun rise in the east and set in the west every day.
The Earth revolves around the Sun. A single revolution takes one year (364¼ days – we make up the
quarter by inserting an extra day in February every four years and call that a “leap year”).
We have seasons on Earth because the axis of the Earth is tilted toward Polaris (the North Star) while it
revolves around the Sun. The tilt causes seasons by changing the amount of sunlight and the intensity of
that sunlight at the same time. When it is summer in NY, the axis is tilted toward the sun so the days are
longer and sunlight is more direct/intense. When it is winter in NY, the axis is tilted away from the sun
so the days are shorter and sunlight is more indirect/weaker.
Seasons are caused by the Tilt of the Earth’s Axis!
The moon rotates and revolves around the Earth. It takes the moon about a month (28 days) to rotate and
revolve around the Earth. Since we see the moon from the reference of point of Earth, we see a slightly
different amount of the lit side of the moon every night. We call the lit portions of the moon that we see
Phases of the Moon.
The tides are created by the gravitational pull of the moon on the Earth’s oceans. There are two types of
tides: spring tides with a big difference between high and low tides (these happen when the
Earth/Sun/Moon are all oriented in a straight line) and neap tides where the difference between high and
low tides is slight (these happen when the Earth/Sun/Moon are at right angles.
Mapping
Latitude and Longitude: Latitude and longitude is used to show an exact location on Earth. Latitude is
measured in degrees north and south of the Equator and the lines run from left to right across the Earth.
Longitude is measured in degrees east and west of the Prime Meridian and the lines run up and down
across the Earth. You always write a location as the latitude followed by the longitude (just like latitude
comes before longitude in the dictionary). The location of Newburgh is: 41.5197° N, 74.0214° W
Earth Science Unit
Review Summary
Topographic Maps are isoline maps, meaning that the lines on the map all touch points that are equal, in this case, in
elevation. There are lines with marked elevations above sea level and unmarked lines. To tell if the land is rising or
falling, look at two marked lines and determine if the elevation between two points are going up or going down.
Lines that are close together indicate that there is a steep slope and lines that are farther apart indicate a gentler
slope.
Plate Tectonics
The face of the Earth is constantly changing very slowly. The Theory of Plate Tectonics tells us that the lithosphere
of the Earth (made up of the crust and the solid mantle) is made up of large plates, which move because of the
convection currents in the plastic/liquid part of the mantle. The boundaries where lithospheric plates meet have
interesting features as follows:
Plate boundary
Interesting Features
Example
Transform (where plates
Earthquakes, tsunamis and fault lines when the plates
San Adreas Fault, CA
slide past each other)
move
Convergent (where plates
move toward each other)
Continental-Continental
Mountain building occurs when the plates cause
Himilayan Mountains,
enough force for the rock to bend and fold
Nepal, India
Continental-Oceanic and
Volcanoes form when the oceanic plate subducts and
Mt. St. Helens, WA
Oceanic-Oceanic
melts
Divergent (where plates
move away from each other)
Continental
Rift Valleys
Iceland, Eastern Africa
Oceanic
Mid ocean ridges making up a small seam of volcanoes Mid-Atlantic ridge
Rocks and Minerals
Rocks are made up of minerals. Minerals are naturally
occurring crystalline solids. Minerals can be identified
using a number of physical characteristics like: hardness,
streak, crystal form, and cleavage. Hardness is measured by
the relative hardness with established minerals that are on
the Moh’s Hardness scale. Something that is harder will
scratch something that’s softer. Diamonds are the hardest
known minerals and will scratch all others, including other
diamonds. Streak is the color of the powder left when the
mineral is dragged along an unglazed tile. Different
minerals have different characteristic streaks that may or
may not be the same color as the mineral itself.
There are 3 kinds of rock: igneous (formed by solidification of
magma or lava), sedimentary (formed by the cementation of
sediment), and metamorphic (formed when any existing rock is
exposed to heat or pressure). Rocks are separated into the
categories by the way that they are formed. Rocks can all
change form as shown in the rock cycle diagam.
Weather
Air masses (big “chunks” of air) bring the characteristics of their source
areas where they go. Air masses that form somewhere cold (Polar) bring
cold air, those that form somewhere warm (Tropical) bring warm air. Air
masses that form over water (marine) bring moist, humid air and those that
form over land (continental) bring dry air. When air masses move, those
with different temperatures form fronts (boundaries between different air
masses). You name the front by the temperature of the pushing air mass cold front if cold air is moving in and warm front if warm air is moving in.
The symbols for each front are shown below. The direction of the triangles
or the semicircles point the direction of the movement of the front.
Earth Science Unit
Review Summary