The ice shelf cores, with a total length of 215 meters (705 feet), were long enough to penetrate through glacial ice—which is formed from the compaction of snow and contains air bubbles—and to continue into the clear, bubble-free ice formed from seawater that freezes onto the bottom of the glacial ice. (53, OG)

penetrate /'penɪtreɪt/ v. 进入或穿过某物;充满，遍布

compact /kəm'pækt/ v. 将(某物)紧压在一起

我是分界线，先自己分析哦。

The ice shelf cores, (with a total length of 215 meters(705 feet)),were long enough (to penetrate through glacial ice)—(which is formed from the compaction of snow and contains air bubbles)—and (to continue into the clear, bubble-free ice) (formed from seawater)(tha tfreezes onto the bottom of the glacial ice. )

分析：

大家可以发现，我把句子拆短了之后，就容易理解多了。请大家仔细看我的分析。

修饰一： (with a total length of 215 meters(705 feet))，介词短语，修饰the iceshelf cores，修饰成分一般放后面哦

中文：总长为215米(705英尺)

修饰二：(to penetrate through glacial ice)，非谓语动词

中文：穿透冰川冰

修饰三：(which is formed from the compaction of snow and contains air bubbles)，从句，修饰glacial ice，修饰成分一般放后面哦

中文：由压缩的雪形成的并包含气泡

修饰四：(to continue into the clear,bubble-free ice)，非谓语动词

中文：继续进入清澈的、没有气泡的冰

修饰五：(formed from seawater) ，非谓语动词，修饰the clear, bubble-free ice

中文：由海水形成

修饰六：(that freezes onto the bottom ofthe glacial ice.) ，从句，修饰seawater

中文：凝固在冰川冰底部

主干：括号外面的，The iceshelf cores were long enough，主和谓语中间被解词短语with a total length of 215 meters (705 feet)隔开了，大家要注意

参考翻译：

总长为215米(705英尺)的冰架核已足以穿透(由压缩的雪形成的并包含气泡)的冰川冰，随后穿透清澈的、没有气泡的冰，这些冰是由凝固在冰川冰底部的海水形成的。

这个句子的主要修饰成分就是介词短语、非谓语动词、从句，大家务必想清楚，每一个修饰成分修饰的是什么，才能看清楚这个句子的结构。