What is a coastline? How is its length measured?

Coastline change refers to the retreat or advance of the coastline due to sea level rise and fall and crustal movement. Due to the influence of sea level rise and fall or crustal movement, the invasion of seawater (transgression) or retreat of seawater (retreat) causes great changes in the coastline. So what is the coastline? How is the length of the coastline measured? Let's learn more about it.

Contents of this article

1. What is the coastline?

2. How is the length of the coastline measured?

3. What are the reasons for the change of coastline?

What is a coastline?

The coastline is the boundary between the ocean and the land. A more precise definition is the line where the seawater reaches the extreme point of the land. It changes with the rise and fall of the tide. Due to the influence of tides and storm surges, the sea water rises and falls, and the sea level is sometimes high and sometimes low. This boundary between the ocean and the land is constantly changing. Therefore, the actual coastline should be a collection of countless sea-land boundaries between high and low tides. It is a belt in space, not a fixed geographical line.

How is the length of the coastline measured?

It is generally believed that the length of the coastline can be measured according to the following different methods and standards:

1. Measure according to the natural length of the coastline, that is, measure the natural length of the coastline curve, draw a sealing line at the mouth of the river, and only calculate the length of the sealing line.

2. Measure along the general direction of the coastline. There are two methods: (1) Draw a series of straight lines along the coastline that are consistent with the general direction of the coastline, measure the length of these straight lines, and use this as the length of the coastline. (2) Draw a series of straight line segments along the coastline according to certain standards. For example, if the coastline bends no more than a certain number of kilometers, draw a straight line at both ends of the bend as a closing line. The length of the straight line segments is the length of the coastline.

What causes coastline changes?

The coastline is the boundary between the ocean and the land. A more precise definition is the line where the seawater reaches the extreme point of the land. It changes with the rise and fall of the tide. Due to the influence of tides and storm surges, the sea water rises and falls, and the sea level is sometimes high and sometimes low. This boundary between the ocean and the land is constantly changing. Therefore, the actual coastline should be a collection of countless sea-land boundaries between high and low tides. It is a belt in space, not a fixed geographical line.

Coastline change refers to the retreat or advance of the coastline due to sea level rise and fall and crustal movement. Due to the influence of sea level rise and fall or crustal movement, the intrusion of sea water (transgression) or the retreat of sea water (regression) causes great changes in the coastline.

1. Due to erosion by sea water, glaciers, etc., the coastline has retreated.

2. Silt accumulates at the river mouth and the coastline expands outward.

3. Due to human factors, land reclamation and the outward expansion of the coastline.