Bob ran down the road.
He fell over.

Bob fell over because he wanted to get to the shop quickly.

The thunder roared.
The hobbits hid.

The hobbits hide because they heard the thunder roar.

Bilbo slept in a cave.
The goblins attacked.

The goblins attack Bilbo because Bilbo slept in their cave.

The cart came to a wheezing halt.
Gandalf strode into the hobbit hole.

Gandalf strode into the hobbit hole because the cart came to a halt.

Jim was interested in the idea.
He rang his friend.

He rang his friend because Jim has a interested idea.

Owls are nocturnal.
This means they are active at night.
They have excellent eyesight.

Owls have excellent eyesight; owls are nocturnal because it has excellent eyesight.