Final answer:
The numerous small channels seen on a delta are known as braided channels, which form due to variations in river flow and high sediment loads, causing the river to split into multiple shallow, interwoven channels.
Step-by-step explanation:
The numerous small channels that run over a delta in multiple directions are called braided channels. These small, interweaving channels can be found on deltas where the sediment load is very high and the river flow is variable. This geomorphological phenomenon occurs typically when the waters of a river slow down as they enter a plain, causing sediment to be deposited and the river to split into multiple shallow channels that can form and disappear over time. A well-known feature on Earth, braided rivers can also be observed on other planetary bodies, such as Mars, where they offer clues about past hydrological activity and climate conditions.
Runoff channels, as referenced in the provided information, are indicative of surface runoff from ancient rain storms and suggest a different climate in the past. By examining crater counts, scientists can estimate that these channels are older than the lunar maria and approximately 4 billion years old, hinting at the historical presence of liquid water on Mars and contributing to our understanding of Martian geological history.