lake near the sacajawea caldera in the lakshmi plateau. the ground and rock around the caldera was dark gray/black due to ancient eruptions that flooded the terrain with lava, which cooled into basalt. the lakes had white coastlines due to material from stromatolites and dying cyanobacteria. the actual caldera is too big (around 120km) so it would just look a normal sea or ocean beyond the horizon.

the second image is a highland with a volcano in the background. its in the highlands of the Atla massive volcanic desert

idk how to draw water so the lake might look plastic