1999 Ford Expedition large Coolant Leak?

99 Ford Expedition, Eddie Bauer, 4WD - Vehicle was operating normally, until taken on a rough gravel mountain road yesterday. Upon stopping and getting out, noticed a trail of fluid behind the vehicle on the road, going back quite a way. Looking underneath, a large leak was pouring antifreeze out, not directly under the engine, but about as far back as the driver's seat, and center (not on one side or the other), and with repeated checks of the coolant reservoir, it had emptied out completely over the course of a few minutes of not moving. The leak was only producing while the engine was running, not while off. The vehicle operated normally all the way back home, about a 45 minute drive, no overheating, no shudders, no noise of any kind, so I would think there's not a significant engine problem, and there's still coolant in the system to keep the engine from overheating. Wondering if this might be an easy fix, a hose that came loose because of the excessive vibration from the rough road, or something more. Haven't had the chance yet to get under the car, and can't take it in until tomorrow. Looking for opinions, estimates, anything?

Replace collant resvesour

Is there an auxilliary heating option for the passengers in the second and or, third row?
The tubes and hoses supplyin it can be leaking, Or why not the heat connections at the firewall? The hoses can leak, the heater can leak, the engine fittings for same at the other end?

Try adding coolant and watch where it comes out.
No mystery then.