Scaremongering is causing unnecessary alarm.

Cause mayhem is an interesting expression.  The Concise Oxford Dictionary defines mayhem as “crime of maiming a person so as to render him partly or wholly defenceless” and gives a figurative meaning of “violent and damaging action”.

Cause a stir means excite people’s interest.  Stir in this sense is move.

Cause a riot can be used figuratively.  Once when I was baby-sitting some lively children, I told them I had come to “Read the Riot Act”.

Cause ructions.  A ruction is a disturbance.

A lost cause is a “hopeless undertaking”, whereas a forlorn hope is a “desperate enterprise”.  (Dictionary definitions)

It’s for a good cause is an introduction to a request for charitable giving or reason for going to a lot of trouble.

I have cause to… I am being reasonable in wishing to complain.

I have grounds to… The foundation of my complaint is firm.

Firm ground is what those who have been to sea disembark onto.

Terra firma is how it is said in Latin.

Keep your feet on the ground.  Don’t get carried away.

Ground-breaking work is done on building sites or at the start of a new venture.  Pioneers have to do a lot of preparatory work.

Grassroots are under the soil out of sight.  At grassroots level refers to ordinary people, who do not make themselves noticed.

Earth, air, fire and water were considered to be the four elements.

It can’t have vanished into thin air!
I can’t count how many times I have heard this expression when something had been mislaid.

Jesus told some stories about lost things.  Luke 15