I have a website which requires user to login. And since all the content is not available over https, we have decided that we will use https only for the login page.

All other data's submitted on the page are not sensitive and needn't be encrypted.

Can this approach compromise user's login credentials? Having all other pages on http - can an attacker get access to the credentials from the user session cookies?

I could see many sites having this approach so I think it might be safe - but would like to understand the technicalities behind it.