Drivers were caught in queues that at one stage stretched from Charing Cross to the Erskine Bridge.
Three vehicles were involved in a crash at Junction 17, near Charing Cross, shortly after 7.20am.
Ambulances rushed to the scene and a man was taken to Glasgow Royal Infirmary. His injuries were not thought to be life-threatening.
About 10 minutes later, a car and a fuel tanker crashed near Jct 15 at Townhead, and forced the closure of two lanes.
Police said the woman driver of the car was taken to the Royal Infirmary and treated for "minor injuries".
The crashes meant traffic soon tailed back to Junction 30 Erskine.
Both incidents also meant traffic heading into the city centre on the M77 from Ayrshire and Newton Mearns was stuck because drivers using that road could not get on to the M8.
With the motorways at a standstill, some drivers were left to queue for more than an hour.
A police spokeswoman said: "Officers were called to reports of two collisions.
"The first took place at 7.20am at Junction 17 and, at 7.30am, we received a report of a collision between a car and a fuel tanker at Junction 15.
"Officers were on the scene to recover vehicles."
The carriageway was not cleared until 8.30am and it took a while before the long queues were cleared.