the outside layer of earth is broken up into giant pieces called tectonic plates .

over millions of years these plates move , bump together , overlap , and slide past each 

other , in the process making new areas of ocean floor , building mountains , causing 

earthquakes, and creating volcanoes.



earthquakes


most earthquakes happen where tectonic plates rub against each other ,  in place called "faults".

some fault move with a steady , very gradual creep. in other places , a length of fault can remain

"locked" for years , decades , or centuries ,before  giving  way in a few seconds.

earthquakes are caused by the shaking of the ground after a rupture

like this . the shallower the depth where the rupture begins, the more 

severe the shaking is at the surface.


measuring quakes


the magnitude of an earthquake is a measure of the energy it releases it can be measured using the moment magnitude scale, where a difference of one point corresponds to a 30-fod difference in energy. the intensity of an earthquake can be measured using the Mercalli intensity scale, which grades earthquakes from 1 to 11, according to their effects.


lava








HOT, MOLTEN ROCK THAT FLOW ACROSS THE GROUND IS
CALLED LAVA. IT KEEPS THIS NAME EVEN AFTER IT HAS COOLED
DOWN AND SOLIDIFIED INTO ROCK . LAVA COMES  IN DEFREENT 

FORMS DEPENDING ON WHAT IT IS MADE OF, HOW STIFF OR 


RUNNY IT IS, AND HOW FAST IT FLOW




PAHOEHOE LAVA
 

THIS IS A BASALT LAVA  WITH AN UNBROKEN

SURFACE . AS IT FLOWS, ITS SURFACE  SKIN IS GRADUALLY 

STRETCHED. THE END RESULT CAN END UP OOKING

EITHER SMOOTH OR ROPE- LIKE.



BLOCKY LAVA 







THESE CHUNK OF LAVA FORM WHEN STIFF-
FLOWING LAVA BREAKS UP INTO ANGULAR BLOCKS. 
THESE LAVA BLOCKS HAVE SMOOTHER FACES THAN 
A"A LAVA