How to clear the scrollback in the screen command?

Question

I use the screen command for command-line multitasking in Linux and I set my scrollback buffer length to a very large value. Is there a key combination to clear the

Answer 1

• C-a C will clear the screen, including the prompt
• clear (command, not key combination) will clear the screen, leaving a prompt

ETA: misread the original question; these will just clear the visible text, but will not clear the buffer!