in the early days of the solar system, many planetesimals orbited the sun. theory has it that one large planetesimal the
size of mars struck a glancing blow to the molten earth. how did this event contribute to the formation of the moon?

This event led to the breaking away of a part of earth and the part was held on by earth’s gravity and this part became the moon.

Explanation:

The formation of moon was after the formation of the earth. In the initial years of the formation of earth it was affected by several asteroid hits and comets. Small planets referred to as planetesimals  also kept continuously affecting the earth. Before 4.5 billion years ago a planetesimal which was about the size of Mars hit earth.

This hit led to the breaking away of a part of earth. The part which was sent to space by the hit was caught by the gravity of the earth and the part started orbiting around the earth. The similarity of the rocks in moon to that of earth is attributed to the fact that moon was actually formed from earth.

The moon and earth keeps influencing each other. The moon’s effect reduced the speed of earth’s rotation and the moon keeps moving away from the earth due to the influence of earth.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.