I’ve alway been interested in plate tectonics. To keep things short
and simple, I’ll just cover different types of plate boundaries.
Plates are always pushing against each other (collision boundaries),
pulling apart (diverging boundaries), or going over/under another
(subduction boundaries. What type of boundary exists in a certain
location is dependent upon the movement of each plate and their
thickness. Generally speaking, continental (land) plates are a lot
thicker than oceanic plates. I’ll cover some basics here:
Two Land Plates: This is the simplest plate boundary. The
movement forces the edge of each plate to move upward, forming
mountains. A great example of this would be how India is pushing
up against China. This formed the “large” mountains in Nepal.
Two Ocean Plates: As I mentioned, ocean plates are thinner that
land plates. One ocean plate is pushed under the other. This ends
up creating magma under the top plate. Water from the ocean is
sucked down with the Earth. This generates cone (aggressive)
volcanoes and a trench where the lesser plate is sucked under.
Check out the Mid-Atlantic Ridge on Wikipedia or something.
Land/Ocean Collision: Again, the thickness of the plates come into
play here; the ocean plate is almost always shoved under the land.
Magma is again formed from the heated and buried Earth. Cone
(aggressive) volcanoes form along these regions and a trench is
formed not far off the coast. Check out the ring of fire.
Two Land Plates: When two land plates pull apart, the link between
them is weakened. This provides a path for magma (turning into
lava upon emerging) to come up. Volcanoes form, but I’m not sure
if they are cone (aggressive) volcanoes or shield (calm). I’d guess
Two Ocean Plates:Same thing here, except under water. These ones
are definitely shield volcanoes. Are great example of this is the
Hot-Spot (Mantle Plume): When you’ve got a hotspot in the Earth
and a (thin) ocean plate is rolling over it, an Island chain will form.
This process is very slow. The older islands, due to Erosion, are
much smaller. The most obvious example (and the only one I can
think of right now) is Hawaii.
Sliding: This is a boundary where two plates are “sliding” against
one another but not directly impacting or pulling away. You’ll get a
fault here and an increased risk of Earthquakes (thus Tsunamis if
it’s near water). Check out the San Andreas Fault.
Puzzle-Fit: A lot of cartographers use this to an awesome extent,
and most also know what it is. You’ll see it with South America and
Africa; the continents look like they fit together because of the
plates moving apart.
--->Why do plates move? Plates, like many things here on Earth,
move because of convection currents. This is (essentially) when
something hot rises and cools when it falls. Think of a lava lamp.
Currents such as this also drive the wind and waves (I might talk
about that later). The half-molten rock that is part of the Earth’s
crust is also moving, albeit slowly. This movement causes the
plate movement we see today.
--->If plates are being melted at some boundaries, how is a plate
formed? In essentially the same way! Underwater volcanoes,
especially, contribute to the formation of ocean crust. All of the
rocks on Earth are just in a really slow cycle.
--->Do plates change their directions of movement (and, if so,
how?) Well, check out the below pic; it’s of the hotspot that created
the Hawaiian Island Chain. What’s cool is that it bends! That suggests
change in movement. Plate traffic-jams can cause massive change
in plate movement across the world. There may be other reasons.
Plate Movement Animation Here you can find an animation of the plate
movement over the past 150 million years! This is a popup (potentially).
Island Chain Animation Here is an animation
of how an island chain forms, featuring a hotspot. This link
opens a text page; click the image on that page.
If you’re using this for a project, please check my research with some of
your own. There’s a chance I jumbled something up here. Let me know
if I did; I’ll edit it.
If you have a further question or such, ask it! Send me information and
I might edit it into this post. The goal of this thread is to be a hub of
resources for the making of scientifically accurate maps.