The Gulf of Finland is a part of the sea. 

The Gulf of Finland is a part of the sea. 
The water is not very salty. This is because many rivers flow into it. One big river is called the Neva. 
In the winter, the water can turn to ice. This happens from late fall until spring. The ice starts in the east and moves west.
Many animals live in the gulf. Grey seals like to live on some islands. 
It is a very busy place for ships. It is a special part of our world.
The Gulf of Finland is a part of the Baltic Sea. 
The gulf is not very deep. The water gets shallower as you move east. 

Many kinds of fish live in these waters too. You can find salmon, cod, and herring. People use the gulf for fishing in spring and autumn. The gulf is also a busy place for ships. It has many important harbors for trade. 
The Gulf of Finland is a large arm of the Baltic Sea. 

The water in the gulf is quite shallow. The depth gets smaller as you move toward the east. The average depth is only 38 meters deep. In the Neva Bay, the water is even shallower. Because of this, a new channel was dug in 2019. This helps ships travel safely through the shallow bottom. Many rivers flow into the gulf from all sides. The Neva River provides two-thirds of all the fresh water. This makes the gulf water much less salty than the ocean. 
History shows that many people have lived here for a long time. People found sites on the shores that are 9,000 years old. These early people were hunters who used tools made of quartz. Later, different groups like the Swedes and Russians fought for control. Russia built nineteen artificial islands with forts to defend its lands. They did this during the Great Northern War around 1700. One famous fortress city is Kronstadt, built on an artificial island. 
Nature is very active in these cold waters. The weather can be quite harsh with strong western winds. These winds often cause big waves and floods. In the winter, the gulf can freeze completely. This usually happens by late January. 
The gulf has many interesting shapes and features. The northern coast is high and has many small bays. The southern shores are smoother and more shallow. Along the southern coast, there is a high limestone cliff. This cliff is called the Baltic Klint. The gulf is full of many islands and small rocks. Some of these islands are home to large cities. For example, Kotlin Island is home to the city of Kronstadt.
The Gulf of Finland is the easternmost arm of the Baltic Sea. 

The physical shape of the gulf is defined by its changing depth and width. The length of the gulf runs from the Hanko Peninsula to Saint Petersburg. Its width varies significantly across the water. It is wider near the entrance to the Baltic Sea. However, the width decreases as it reaches the Neva Bay. The water is relatively shallow throughout the region. The average depth is 38 meters. The maximum depth reaches 143 meters. The depth decreases as you move toward the eastern end. A sharp change in depth occurs near Narva-Jõesuu. This specific area is known as the Narva wall. In the Neva Bay, the depth is less than 5 meters. Because of this, a channel was dug in March 2019 to allow for safe navigation.
Water chemistry and climate also define this environment. The gulf has very low salinity, which means it is not very salty. This is because of the large influx of fresh water from many rivers. The Neva River is the largest contributor, providing two-thirds of the total runoff. Surface salinity stays between 0.2 and 0.3 parts per thousand. Near the bottom, it is slightly higher at 0.3 to 0.5 parts per thousand. The temperature of the water changes with the seasons. In winter, the average temperature is close to 0 degrees Celsius. In summer, surface temperatures reach 16 degrees Celsius. 
The coastlines of the gulf offer different views. The northern coast is high and winding. It features many small bays and skerries, which are small rocky islands. There are only a few large bays, such as Vyborg. The northern shores also include the Hanko and Porkkalanniemi peninsulas. The southern shores are smoother and shallower. However, a limestone escarpment called the Baltic Klint runs along the southern coast. This cliff can reach heights of up to 50 meters. The gulf is filled with many islands and banks. Large islands include Kotlin Island, which holds the city of Kronstadt. Other notable islands are Gogland, Naissaar, and Maly Vysotsky.
Geological history shaped the modern depression of the gulf. Long ago, during the Cenozoic era, large rivers eroded the land. These rivers cut through sedimentary layers of claystone and sandstone. As they eroded deeper, they hit harder Ordovician-aged limestone. This process helped form the Baltic Klint cliffs. Later, glacier activities reshaped the area. When the glaciers retreated, they formed the Littorina Sea. The water level then was 7 to 9 meters higher than the modern Baltic Sea. About 4,000 years ago, the sea receded. This recession turned many underwater shoals into the islands we see today. The uplifting of the Baltic Shield also caused the northern shores to be higher than the southern ones.
Human history in the gulf is very long. Archaeological sites show that people lived here 9,000 years ago. These early inhabitants were hunters who used quartz tools. Later, various groups like the Estonians, Votes, and Izhorians lived along the coasts. Between the 8th and 13th centuries, the gulf was a major waterway connecting Scandinavia to the Byzantine Empire. Many wars were fought here for control. During the Great Northern War (1700–1721), Russia fought to secure the area. To protect Saint Petersburg, Russia built nineteen artificial islands with fortresses. These included Fort Alexander and Krasnaya Gorka. The city of Kronstadt was also built on an artificial island to control the waterway. 
Nature thrives in these waters despite the harsh conditions. The vegetation includes coniferous and deciduous forests. Common trees are pine, spruce, birch, and willow. In the eastern marshy areas, you can find reeds and waterlilies. Many fish species live in the gulf. These include Atlantic salmon, Baltic herring, Atlantic cod, and northern pike. Commercial fishing happens in the spring and autumn. The gulf is also a home for marine mammals. Grey seals live on the Malusi islands. 
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