How are Earthquakes and tsunami's alike and different?

Sounds like the teacher is asking a rather absurd question--- earthquakes cause tsunamis, so comparing/contrasting makes no sense. I make spit but don't compare me to spit!  Really really strange for a 2nd grader to have to answer.

Alike:
Tsu. are waves on water, quakes make waves on land
Both cause lots of damage
Damage is in a limited area
Instruments can measure the size of both
Both happen without warning

Different
Quakes cause Tsu. but not the reverse
Quakes can happen on land or ocean, but Tsu. occur only on water.
Tsu. can cause damage far away
Tsu. are only longitudinal (surface) waves, quakes have shear and compression waves as well.
Quakes have aftershocks hours or days later, Tsu. only happen once after a quake.

Tough question for 2nd grader -- be interesting in what they come up with.

Alike:
Both are carried with waves (the earthquake is with seismic waves and the tsunami will tidal waves).
Both generated by seismic activity.
Neither can be predicted (well) beforehand.
Both have epicenters
Both are incredibly destructive natural phenomenon
Different:
Earthquakes travel through land while tsunamis travel through water

Sorry that's all I got before it gets a bit complicated, hope I helped.

I taught Earth Science for 27 years, and I'd agree completely with Wildturkey's answer.  This is a very strange question for a 2nd grade class, a bit like asking the kids to compare/contrast asteroids with mass extinctions.