They noted at that timethat only two of the bogs contained palsas, whereas aerial photos takenin 1957 showed palsas present in all of the bogs.
他们注意到那时只有两个沼泽有泥炭丘，而1957年空中拍摄的该地区照片显示所有沼泽都有泥炭丘。
2
Helicopter flyovers between the 51st and 55th parallels alsorevealed that the palsas are in an advanced state of deterioration overthe entire James Bay area.
飞越在北纬51度和53度纬线间的直升机也透露整个詹姆斯湾地区泥炭丘处于严重恶化的状况。
3
The researchers measured the retreat of the permafrost border byobserving hummocks known as "palsas, " which form naturally over icecontained in the soil of northern peat bogs.