A pyroclastic flow (also known scientifically as a pyroclastic density current) is a fast-moving current of hot gas and rock (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph).The gas can reach temperatures of about 1,000 Â°C (1,830 Â°F).Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope.They are a common and devastating result of certain explosive volcanic eruptions.yroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope.
Optimal Reading. An optimal reading is considered anything lower than 120/80. The actual number of 120/80 is not considered perfect--but actually numbers lower are considered to be optimal. For example, someone with a blood pressure reading of 116/76 has an optimal reading.ptimal Reading. An optimal reading is considered anything lower than 120/80. The actual number of 120/80 is not considered perfect--but actually numbers lower are considered to be optimal. For example, someone with a blood pressure reading of 116/76 has an optimal reading.
Blood pressure is shown as two numbers, such as 120/80 (say 120 over 80). The top number is the pressure when the heart pumps blood. It is called the systolic pressure. The bottom number is the pressure when the heart relaxes and fills with blood.It is called the diastolic pressure. An ideal blood pressure for an adult is less than 120/80. High blood pressure is 140/90 or higher. Prehypertension is between 120/80 and 140/90.t is called the systolic pressure. The bottom number is the pressure when the heart relaxes and fills with blood. It is called the diastolic pressure. An ideal blood pressure for an adult is less than 120/80. High blood pressure is 140/90 or higher. Prehypertension is between 120/80 and 140/90.