Transcript 4th grade Earth Science Part 2

TH
4
GRADE EARTH
SCIENCE PART 2
L.O. I will describe what reshapes
land and how this happens.
Day 1 Fast Changes in Earth
• Earthquakes
• *A fault is a crack in the Earth’s crust
• The two sides are called plates
• *During an earthquake, one of three things
will happen:
• the plates push against each other and will
slide along each other
• the plates push against each other and one
side will go on top of the other
• the plates pull apart
• The epicenter is where an earthquake is
felt most strongly
• Tsunami is a very large ocean wave
caused by an earthquake on the ocean
floor
• Volcanos
• Opening in Earth’s crust
• Hot ash, gases, and molten rock escape from
deep within Earth
• Molten rock beneath Earth’s surface is called
magma
• When magma reaches Earth’s surface, it is
called lava
• *Hawaii was formed by volcanoes
• *Landslides – the sudden movement of
loose rock and soil down a steep slope
• The steeper the slope, the faster the
soil and rock will move downhill
• *4 main things cause landslides:
• Heavy rains
• Sudden melting of snow
• Earthquakes
• Volcanic eruptions
Day 2 Slow changes in Earth
• *Weathering is when rocks slowly wear away
into smaller and smaller pieces by water, snow,
wind, and rain
• *Erosion moves these sediments (rock pieces)
that were a result of weathering from one
place to another
• As moving water flows, it loosens and
picks up the tiny particles that have
been left by the weathering and carries
it down stream or to other places –
called erosion
• *Therefore, Moving Water causes
landforms to erode
• *Wind carries bits of rock and soil in the
air – so wind causes erosion
• *Moving water and wind cause erosion
which created Grand Canyon
• *5 things cause rocks to break into
smaller pieces
*The first three are the main causes
1. *Continual freezing and thawing ice
2. *Plant roots
3. *Moving water
4. Heat mixed with rain
5. chemicals
Freezing and thawing
Most rocks have tiny cracks in them
Water gets into the cracks
When it freezes, it expands
Pushes the crack, making it a little bigger
Melts
Refreezes, pushing crack to make it bigger
Eventually this process will cause the rock
to break
• Plant roots
• Roots are small and grow into cracks
• Over time, as the root grows it spreads
the crack wider
• Eventually, the rock will break
• Rocks that are exposed to or in moving
water such as streams constantly bump
against other rocks, wearing down sharp
edges and becoming smooth and smaller