Why does the Gulf of Riga have a shallow and simple shape?

The Gulf of Riga exhibits a shallow and simple shape primarily due to the nature of the underlying geologic structure in the region. Specifically, the presence of homogeneous bedrock that possesses low strength or resistance to erosion leads to the development of these relatively simple, shallow topographic characteristics.1

In such environments, the lack of complex geological resistance allows for a more uniform formation of the coastal feature compared to regions shaped by intense tectonic activity or complex faulting. Additionally, the gulf is characterized by significant siltation, which is common in long or restricted gulfs where sediment accumulation is influenced by river discharge.12