Simplify the following text for a Grade 8 native English-speaking person.
Original: These particles are small , slaggy pieces of magma and rock that have been tossed into the air by outbursts of steam and other gases ; magma may have been torn apart as it became vesicular by the expansion of the gases within it .
Simplified: These particles are small , slaggy pieces of magma and rock that have been tossed into the air by outbursts of steam and other gases .