Tectonic Edge
Land
: Add 
.
, , Sacrifice this land: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.
"We move because the earth does." —Bruse Tarl, Goma Fada nomad
Vincent Proce
Rulings
Tectonic Edge’s second ability checks how many lands an opponent controls only at the time you activate the ability.
(wotc • 2010-03-01)
Assuming you can activate Tectonic Edge’s second ability, you can target any nonbasic land with it (not just one controlled by an opponent that controls four or more lands).
(wotc • 2010-03-01)
Rulings
Tectonic Edge’s second ability checks how many lands an opponent controls only at the time you activate the ability.
(wotc • 2010-03-01)
Assuming you can activate Tectonic Edge’s second ability, you can target any nonbasic land with it (not just one controlled by an opponent that controls four or more lands).
(wotc • 2010-03-01)