How the Boston Harbor Islands formed and How they are changing today

How the Boston Harbor Islands formed and How they are changing today

By:Nicolas SantiagoBy:Nicolas Santiago

GlaciersGlaciers

Millions of years ago, a glacier covered our continent. It retreated and recovered the continent several times.

Millions of years ago, a glacier covered our continent. It retreated and recovered the continent several times.

MeltingMelting

As the glacier melted, it left rock and dirt debris called till. As till built up, it created many different landforms.

As the glacier melted, it left rock and dirt debris called till. As till built up, it created many different landforms.

DrumlinsDrumlins

One landform that glaciers created are called drumlins. A drumlin is a pile of till shaped in the direction that the glacier traveled in. When the glacier melts, water covers the land surrounding the drumlin, creating one of only two drowned drumlin fields in the world.

One landform that glaciers created are called drumlins. A drumlin is a pile of till shaped in the direction that the glacier traveled in. When the glacier melts, water covers the land surrounding the drumlin, creating one of only two drowned drumlin fields in the world.

ErraticsErratics

As glaciers move, they pick up large boulders. When the glacier melts the rocks are dropped in random places.

As glaciers move, they pick up large boulders. When the glacier melts the rocks are dropped in random places.

Erosion by wavesErosion by waves

As days go by, the drumlins are eroded by waves. Because of the way the glacier traveled, one side of the island gets hit harder than the other.

As days go by, the drumlins are eroded by waves. Because of the way the glacier traveled, one side of the island gets hit harder than the other.

ImpactImpact

One way the island is eroded by waves is from impact. The force of the waves hitting the shore break apart rocks. On one side of the island, the shore is in good condition. However on the other side, the rock is broken and scatered due to the fact that one side of the island is facing the open sea.

One way the island is eroded by waves is from impact. The force of the waves hitting the shore break apart rocks. On one side of the island, the shore is in good condition. However on the other side, the rock is broken and scatered due to the fact that one side of the island is facing the open sea.

AbrasionAbrasion

Another way the waves erode the island is by abrasion. Rock and sand and other debris are in waves. When waves hit the shore, they wear down and scrath rock making them smooth, much like the effect sandpaper has.

Another way the waves erode the island is by abrasion. Rock and sand and other debris are in waves. When waves hit the shore, they wear down and scrath rock making them smooth, much like the effect sandpaper has.

DepositionDeposition

Waves pick up debris as they travel. When the waves lose speed, they drop it, making several different types of landforms.

Waves pick up debris as they travel. When the waves lose speed, they drop it, making several different types of landforms.

BeachesBeaches

One result of deposition is a beach. Beaches in Massachusetts are made from eroded rock. Most Boston harbor islands have a beach

One result of deposition is a beach. Beaches in Massachusetts are made from eroded rock. Most Boston harbor islands have a beach

Longshore Drift and SpitsLongshore Drift and Spits

When waves travel at an angle, they deposit sand at an angle as well. These can form landforms such as a spit. A spit is a “finger” of sand that sticks out into the water.

When waves travel at an angle, they deposit sand at an angle as well. These can form landforms such as a spit. A spit is a “finger” of sand that sticks out into the water.

Wind Erosion Wind Erosion

There are many ways wind can cause erosion. Wind by itself is very week eroding. When it blows and there is little vegetation, it picks up loose sand and dirt, or loess, either depositing it in a different location, making large piles of loess, also known as a sand dune. Also when there is loess in the wind, it can scrape a rock smooth, a form of abrasion. Because the Boston harbor islands are exposed in the open, they are eroded by wind everyday

There are many ways wind can cause erosion. Wind by itself is very week eroding. When it blows and there is little vegetation, it picks up loose sand and dirt, or loess, either depositing it in a different location, making large piles of loess, also known as a sand dune. Also when there is loess in the wind, it can scrape a rock smooth, a form of abrasion. Because the Boston harbor islands are exposed in the open, they are eroded by wind everyday

Erosion by WaterErosion by Water

Water is also a major factor in erosion. When it rains, the water can cause many types of things. One result of water erosion are rills and gullies. When rain hits a hill with little vegetation, it flows downhill, forming things called rills. Rills are little grooves in the soil were the water flowed down. When rills connect, they form gullies. Gullies are larger rills were water flows down. When water flows down, the sediment gets caught in the water. This is called runoff.

Water is also a major factor in erosion. When it rains, the water can cause many types of things. One result of water erosion are rills and gullies. When rain hits a hill with little vegetation, it flows downhill, forming things called rills. Rills are little grooves in the soil were the water flowed down. When rills connect, they form gullies. Gullies are larger rills were water flows down. When water flows down, the sediment gets caught in the water. This is called runoff.