Problem: What is the missing first step of the following process: - Under the right conditions it can develop further and start to spin around a low-pressure center - If it develops it's classified as a 'tropical cyclone' or 'tropical depression' - If the system strengthens and wind speeds rise past 39 mph, the system is dubbed a 'tropical storm' - If the pressure in the center drops even further and the winds really pick up and forms a clearly defined 'eye' it's a hurricane -

A: A hurricane usually starts as an organized thunderstorm activity that stretches at least 100 miles across and maintains its identity for more than 24 hours

Problem: What is the missing first step of the following process: - The trees die off - The dead material provides nutrients for more trees - The rising trees provide shelter - And more organisms begin to thrive - The ecosystem known as a forest is made.

A: Networks of trees start forming

Problem: What is the missing first step of the following process: - After a rain, water seeps into cracks and pores of soil and rock - The water percolates beneath the land surface - Some of the water reaches a zone where all the cracks and pores in the rock are already filled with water - Rainwater absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation - The water combines chemically with the carbon dioxide - A weak carbonic acid solution is formed - This acid slowly dissolves calcite, forms solution cavities, and excavates passageways -

A: Solution caves are formed in limestone and similar rocks by the action of water

Problem: What is the missing first step of the following process: - As the plates move, they exert a great force - When the force is large enough, the crust breaks - The stress is released as energy - The energy moves through the Earth in the form of waves - We feel the earthquake -

A:
Plates on the Earth's crust move slowly past each other