可能审稿人没空，或者审稿意见矛盾，编辑又找新的审稿人。

又找了一个审稿人吧

写信问问吧，那么久了

If I understand you correctly, you submitted during Dragon Boat and just now is "under review"?

If you visit the journal main website in Springer   https://www.springer.com/earth+s ... raphy/journal/12517

you will see that the average time to first response is 144 days (almost 5 months to first response). So you are within normal situation with this journal.

Hope this help.  

best regards，

应该是重新找了个审稿人。可能之前有个审稿人没时间审，也可能是已有的审稿人审稿意见不一致，编辑找第三个审稿人。
祝好运

很可能审稿人没有完成审稿啊

引起Under Review日期变化的原因很多，有可能是更换审稿人，追加审稿人，部分审稿意见返回等原因。