"As of mid-March, only a narrow strip of shelf ice was protecting several thousand kilometers of potential further break-up, " the group said.

CNN: Massive ice shelf on verge of breakup

On day three, after about 60km of riding, we crossed the 3, 900m-high Tosor Pass, where a sheer cliff of ice and snow gave way to a narrow corridor with the shimmering Kerege-Tash Valley below.

BBC: The way of the shepherd: Horse trekking through Kyrgyzstan

One theory is that the summer sun melts ice on the surface of the glacier which creates pools of water which then flow into moulins -- narrow tubular shafts in the glacier.

CNN: Rubber ducks aid NASA study