Rock Formation/Rock Cycle
These are some of the tectonics words
and concepts you should become
familiar with.

Tectonic Plate:  A large piece of the
earth's crust that floats on the mantle.

Plate Boundary:  Where two or more
tectonic plates meet.

Continental Crust:  The thicker, but
less dense crust of the continents.  
Mostly made of granite and gneiss.  
Floats higher on the earth's mantle
than oceanic crust does.

Oceanic Crust:  The thinner, but more
dense crust of the oceans.  Mostly
made of basalt and gabbro, with a lot
of ocean sedimentary rocks forming on
top of that.  Much younger than
continental crust.

Convection Currents:  Hot mantle
material rises because it is less dense.  
When it gets near the crust, it cools
and falls because it gets more dense.  
This produces slow moving currents in
the mantle which move the tectonic
plates that are floating on the mantle.

Convergent Boundary:  Where two
plates are colliding.

Subduction:  When an oceanic plate is
sliding under another plate (at a
convergent boundary).  The denser
plate subducts and is destroyed in the
mantle of the earth.

Divergent Boundary:  Where two plates
are moving apart from each other.  
New crust is made at these boundaries.
 Volcanoes with runny basalt lava erupt

Rift Valley = Graben = Rift Basin:  
Divergent continental plates make
these.  A large piece of the crust drops
lower than the surrounding land.  New
crust is formed and if the rifting
continues, a new ocean can open up in
the middle of a continent.

Horst:  The high parts on either side of
a graben.

Half-Graben: When a graben only
drops down on one side.

Failed Rift:  A rift valley that starts to
form, but then stops when the tectonic
forces move to another location.

Mid-Ocean Ridge: Divergent oceanic
plates make mid-ocean ridges, where
magma comes up from the mantle and
cools to form new ocean crust.

Transform Boundary:  Where two
plates are sliding past each other,
neither colliding nor moving away.  
These produce earthquakes.
These are some of the erosion words
and concepts you should become familiar

Erosion:  When forces like water, wind,
ice or gravity pick sediment up and carry
it away.

Deposition:  When forces like water, wind,
ice or gravity no longer have the energy
to carry sediments, they set it down in a

Alluvial Fan: When mountains are eroded
quickly, the sediment that is removed
comes out mountain canyons.  When
those canyons open out into valleys or
other low areas, the sediment spreads
out in a fan shaped deposit.

Abrasion: When gritty things like sand
rub against rocks or bedrock, they
scrape pieces of it off, like sandpaper
does.  These scrapes are called
abrasions, and they wear down surfaces.

Clastic: When bedrock is broken into
smaller pieces, those pieces are called
"clasts."  Clastic means made of pieces.  
Clasts can be any size from boulders to
sand to tiny clay particles.

Pothole: When water currents move
gravel or sand around in a low part of the
rocks at the bottom of a stream, they can
start spinning.  Over time, the
combination of current and scraping
rocks acts like a drill which grinds out a
hole in the bedrock.  That hole is a
These are some of the glacier words and
concepts you should become familiar with.

Glacier:  A large piece of ice and snow which
flows under its own weight.

Valley Glacier:  A glacier that fills a valley.

Continental Glacier:  The combination of many
glaciers that actually flow OVER most
mountains and cover large parts of a continent.

Polishing:  The smoothing of bedrock by
glaciers going over them.  Glaciers are full of
tiny rock flour which polishes any surface they
move over.

Striations:  Scrapes made on bedrock by
glaciers dragging stones or boulders across
the surface of the bedrock.

Erratic:  A boulder or stone that is carried by a
glacier and dropped in a new place.

Moraine:  A hill of glacial deposits pushed in
front of a glacier or left on the sides of the
glacier.  The sediment is mixed up and
unsorted and resorts itself over time, making it
an unstable place to build.

Esker: A long snaky hill that is left behind from
a stream that flows UNDER a glacier.  When
the glacier melts away, the deposits that filled
an ice cave are left behind.

Kettle Pond:  A pond made when a chunk of a
melting glacier falls of the glacier, gets buried
by outwash sediments, and then melts.  The
melted chunk of ice leaves a hole.  If it is below
the water table, the hole fills with water,
making a kettle pond.  If the hole doesn't fill
with water, we just call it a kettle hole.
Igneous:  Rocks made from cooling
molten rock.  (Can be above or below

Metamorphic:  Rocks changed from one
type to another by heat and pressure.

Regional Metamorphic Rocks:  Rocks
changed by heat and pressure effecting
a large area.  This is usually because of
tectonic activity like convergent
continental plates running into each
other an making mountains.

Sedimentary:  Rocks made of sediment.  

Clastic/Detrital Sedimentary Rocks:  The
sediment can be clastic or detrital (made
of pieces), which makes clastic
sedimentary rock.  

Chemical Sedimentary Rocks:  The
sediment can also be made of dissolved
minerals, which make chemical
sedimentary rocks.  

Organic Sedimentary Rocks:  The
sediment can also be made of dead plant
or animal material, which makes organic
sedimentary rocks.

Limestone:  A chemical sedimentary rock
that forms in shallow seas when sea
shells or dissolved sea shells are
deposited on the sea floor.

Marble:  A metamorphic rock that is
formed when limestone is heated and

Sandstone: A clastic or detrital
sedimentary rock made of SAND.

Conglomerate:  A clastic or detrital
sedimentary rock made of gravel or
larger clasts (pieces of rock).

Basalt:  A dark and dense volcanic
igneous rock formed at divergent plate
boundaries like rift valleys and mid-ocean
ridges.  Hot-spot volcanoes also produce

Gneiss:  A metamorphic rock that is
formed when other types of rock are
buried about 12 kilometers under
ground.  That kind of pressure is only
produced when mountains are being built
by convergent continental plates.