6. LATHER US (anagram)
7. Separates the scots and the English
11. In which continent are the Atlas Mountains
17. Dormant volcano and second highest peak in Mexico
18. A CARS IN THE PATH (anagram)
23. The principality of Andorra is located in these mountains
argorstran - flor de Orizaba is the highest mountain in Mexico, and is a dormant volcano.
The second highest peak is Popocatépetl which is an active volcano, so I'm not sure which is required here.