​The Plagues are thought to have happened around the same time as a massive volcano eruption (1400-1650BC). The volcano Santorini sent ash in to the air effecting the surrounding area, including the Nile River.  

1st Plague. River ran red LIKE blood. But there is a common algae plume called the Red Tide (or Oscillatoria Rubescens ). This makes the river, or any water, look red like blood. Why did this happen? The ash changes the PH level of the river allowing the algae to bloom.

2nd Plague. Frogs. The algae is killing fish. So that means we had fewer fish, and yet a record number of frogs. The frogs couldn't live in polluted water and so they left the river.

3rd and 4th Plagues. Lice and flies. So the insect plagues may have been a result of the river full of dead fish (and dead frogs). 

5th and Plagues. Pestilence and boils may have been brought on by the insect bites that could have gotten infected.

7th Plague. Fire and Hail. Ash in the air causes a mixture of ash and water. The ash, very high in the air, can cause the water to freeze so when it falls it is hail and not rain. Red lightning (known as sprites) can sometimes come from chemicals in the ash. The red color is produced from the excitation of the gas molecules in the atmosphere, particularly nitrogen.

8th Plague. Locusts. Locusts come about when the ground is very damp and they bury their eggs in the sand about 4-6 inches. After record amounts of hail the ground could be very wet allowing the locusts to form.

9th Plague. After an eruption, the ash in the air can remain for a while causing darkness. 

10th Plague. Death of First born. In Egypt the first born was king. When food was scarce the first born was fed first and sometimes was the only one to eat. After locusts ate every thing there was only grain locked in vaults. The hail got it wet and made it moldy. And so when only the first born ate, they were the only ones killed by moldy grain. 

haggadah Section: -- Ten Plagues
Source: National Geographic