It is always helpful to provide context such as a link to the original material. (BBC article) https://www.bbc.com/future/article/20200115-what-the-earliest-life-on-earth-looked-like 1) Some 560 million years ago, the Earth was THAWING ITS WAY OUT of an ice age [= Some 560 millions years ago, an ice age was gradually ending as the Earth warmed up.] The Earth was thawing [standard English - just like "the frozen vegetables were thawing"] The Earth was thawing its way out of ... by analogy to "working its way out of " ... [gradually] Oxford Learner's Dictionaries website https://www.oxfordlearnersdictionaries.com/definition/english/work_1?q=work meaning 14 - move gradually ​[intransitive, transitive] to move or pass to a particular place or state, usually gradually + adv./prep. It will take a while for the drug to work out of your system. 2) The site is remarkable IN THAT IT IS one of the only places ... [= The site is remarkable because it is one of the only places ...] Oxford Learner's Dictionaries website: https://www.oxfordlearnersdictionaries.com/definition/english/in_1#in_idmg_1 in that ​(formal) for the reason that; because

THAWING ITS WAY OUT To thaw: slowly become not frozen OR slowly warming up above freezing temperatures The sentence then becomes: Some 560 million years ago, the Earth was slowly warming up from an ice age. IN THAT IT IS a set of words to begin the reason for a statement. It can be similar to "because". This is a style choice of the writer. The sentence can be rearranged or reworded : The site is remarkable because it is one of the only places that records the transition between the Ediacaran and Cambrian periods.

Hey Oliver, thank you... "because" sounds like a better option than "in that"

1) Thawing its way out: the ice was melting and ice age was coming to an end. To thaw means that something is coming out of being frozen. 2) in that it is: a way of saying “It is remarkable because...”. “In that” is a way of saying “here is why we are saying this”