Why the Strait of Hormuz Is Such a Question Mark

It's less a million-dollar question and more a billion-dollar one: Will Iran move to close the Strait of Hormuz? About 20 million barrels of oil—amounting to about 20% of global oil and gas—flow through the strait daily by the US Energy Information Administration's count, and Reuters reports Secretary of State Marco Rubio cautioned that "it's economic suicide for them if they do it. And we retain options to deal with that." The latest:

• The process: USA Today reports Iran's parliament voted in favor of a measure to close it, but it doesn't have the final say. Iran would need to secure approval from its Supreme National Security Council, which an appointee of Supreme Leader Ayatollah Ali Khamenei oversees, to do so.
• The logistics: The BBC reports that under UN rules, countries are permitted to control waters up to 12 nautical miles (13.8 miles) from their coast. At its narrowest point, the Strait of Hormuz and its shipping lanes fall solely within Iran and Oman's territorial waters. Experts tell the BBC that should Iran want to prevent all shipping traffic, "one of the most effective ways" to do so would be to "lay mines using fast attack boats and submarines."

• The implications: Per Reuters, "Attempting to strangle the strait could send global oil prices skyrocketing, derail the world economy and invite conflict with the US Navy's massive Fifth Fleet that patrols the Gulf from its base in Bahrain." CNN reports a closure could cause "an existential crisis" for the global oil market.
• An ask of China: The BBC reports Rubio on Sunday called on the Chinese government to urge Iran not to close the waterway. In terms of leverage, China buys more oil from Iran than any other nation—roughly 1.8 million barrels per day in May. The BBC's take: "Beijing is highly unlikely to welcome any rise in oil prices or disruptions to shipping routes."
• A word of caution from the EU: The Guardian quotes top EU diplomat Kaja Kallas as saying, "Closing of the strait of Hormuz by Iran is something that would be extremely dangerous and not good for anybody."
• The financial consequences: The Washington Post sees analysts as largely doubtful Iran will actually close the strait, but should it do so, prices would likely surge north of $100 a barrel (they're at about $75 today), with the price of a gallon of gas likely jumping to $4.
• A historical note: The BBC reports that while Iran has threatened to close the Strait of Hormuz in the past, it has never actually done so.

(More Strait of Hormuz stories.)