Why doesn't New Zealand build a cross-sea bridge between its North and South Islands?

New Zealand is located southeast of Australia, across the Tasman Sea, about 1,600 kilometers away. New Zealand is an island country with an area of ​​about 270,000 square kilometers. It has two main islands: North Island and South Island, with the Cook Strait in between. The North Island has an area of ​​about 113,700 square kilometers, and the South Island has an area of ​​about 150,400 square kilometers.

If you have no idea about the scenery of New Zealand, you can revisit "The Lord of the Rings". The Shire where the Hobbits live in the movie was filmed in New Zealand. However, our topic today is not the natural scenery of this country, but why not build a bridge to connect its North and South Islands?

Today, as bridge-building technology is quite mature, building cross-sea bridges is not a rare thing. The Crimean Bridge between the Black Sea and the Sea of ​​Azov, the English Channel Undersea Tunnel, China's Hangzhou Bay Bridge and the Hong Kong-Zhuhai-Macao Bridge are all typical examples. What is strange is that facing the Cook Strait, which is not very wide, New Zealanders have not yet intended to build a bridge. What is the reason?

The Cook Strait runs from northwest to southeast, and its narrowest point is only about 22 kilometers. When the weather is good, the two islands can easily see each other across the strait. The average water depth of the Cook Strait is 128 meters, and the deepest is about 400 meters. In comparison, the average depth of my country's Bohai Strait is only more than 20 meters, and the deepest is about 86 meters. Although it is 90 kilometers long, there are many small islands in the middle, such as the Miaodao Islands, so it is less difficult to build a cross-sea bridge than the Cook Strait.

Let's look at the Hangzhou Bay Bridge in my country. Hangzhou Bay is a trumpet-shaped estuary formed by the Qiantang River entering the East China Sea. To the north are Jiaxing, Zhejiang and Shanghai, and to the south is Ningbo, Zhejiang. In 2008, the Hangzhou Bay Bridge was completed and opened to traffic, shortening the land distance between Shanghai and Ningbo by 120 kilometers.

The Hangzhou Bay Bridge is a component of the Shenyang-Haikou Expressway. The bridge starts from the Haiyan hub in Jiaxing City in the north, crosses the Hangzhou Bay, and ends at the Andong hub interchange in Ningbo City in the south. The total length of the route is 36 kilometers. The bridge deck is a six-lane bidirectional expressway with a design speed of 100 kilometers.

The Cook Strait is only 22 kilometers at its narrowest point. If a bridge is built, it may be shorter than the Hangzhou Bay Bridge, but the engineering difficulty will be different.

New Zealand is located in the Pacific Ring of Fire, at the junction of the Indian Plate and the Pacific Plate, with frequent volcanic earthquakes. Both the South Island and the North Island of New Zealand belong to two major plates, and the North Island also has a sub-plate of the Pacific Plate, the Kermadec Plate. The Cook Strait is located on the boundary between several major plates.

Hundreds of thousands of years ago, the North and South Islands of New Zealand were connected. A geological fault formed the Cook Strait. There are cliffs below the water surface, and this large crack is slowly expanding. The seabed of the Cook Strait is not stable. From a geological and engineering perspective, the difficulty is really thorny.

Why don't New Zealanders follow the example of Britain and France and build an undersea tunnel, so that they can avoid complex sea conditions? In addition to the difficulty of the project, the cost is also astronomical. The construction and operation costs of tunnels are much higher than those of bridges.

Construction difficulty is only one of the many factors to be considered in bridge projects. The main reason why the "Cook Strait Bridge" has stalled is the input-output efficiency of the project itself.

New Zealand has a population of only 5 million, three quarters of which are concentrated in the North Island. Currently, the ferry between the two places has met the communication needs of both sides. If you want a faster way, you can take a plane. For the cost-conscious New Zealanders, building a bridge at a huge cost is unaffordable.

Perhaps with the development of the times, if New Zealand's population is ten times what it is now, reaching more than 50 million, then building a bridge between the North and South Islands will have a significant economic value, and New Zealand may really build a cross-sea bridge.

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