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.
The diastolic blood pressure number or the bottom number indicates the pressure in the arteries when the heart rests between beats. A normal diastolic blood pressure number is 80 or less. A diastolic blood pressure between 80 and 89 is normal but higher than ideal.A diastolic blood pressure number of 90 or higher, on repeated measurements, is considered to be hypertension or high blood pressure. normal systolic blood pressure is 120 or below. A systolic blood pressure of 120-139 means you have normal blood pressure that is higher than ideal, or borderline high blood pressure.